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infer_4_30_0/lib/python3.10/site-packages/scipy/differentiate/__init__.py

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+"""
+==============================================================
+Finite Difference Differentiation (:mod:`scipy.differentiate`)
+==============================================================
+
+.. currentmodule:: scipy.differentiate
+
+SciPy ``differentiate`` provides functions for performing finite difference
+numerical differentiation of black-box functions.
+
+.. autosummary::
+   :toctree: generated/
+
+   derivative
+   jacobian
+   hessian
+
+"""
+
+
+from ._differentiate import *
+
+__all__ = ['derivative', 'jacobian', 'hessian']
+
+from scipy._lib._testutils import PytestTester
+test = PytestTester(__name__)
+del PytestTester

infer_4_30_0/lib/python3.10/site-packages/scipy/differentiate/_differentiate.py

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+# mypy: disable-error-code="attr-defined"
+import warnings
+import numpy as np
+import scipy._lib._elementwise_iterative_method as eim
+from scipy._lib._util import _RichResult
+from scipy._lib._array_api import array_namespace, xp_sign, xp_copy, xp_take_along_axis
+
+_EERRORINCREASE = -1  # used in derivative
+
+def _derivative_iv(f, x, args, tolerances, maxiter, order, initial_step,
+                   step_factor, step_direction, preserve_shape, callback):
+    # Input validation for `derivative`
+    xp = array_namespace(x)
+
+    if not callable(f):
+        raise ValueError('`f` must be callable.')
+
+    if not np.iterable(args):
+        args = (args,)
+
+    tolerances = {} if tolerances is None else tolerances
+    atol = tolerances.get('atol', None)
+    rtol = tolerances.get('rtol', None)
+
+    # tolerances are floats, not arrays; OK to use NumPy
+    message = 'Tolerances and step parameters must be non-negative scalars.'
+    tols = np.asarray([atol if atol is not None else 1,
+                       rtol if rtol is not None else 1,
+                       step_factor])
+    if (not np.issubdtype(tols.dtype, np.number) or np.any(tols < 0)
+            or np.any(np.isnan(tols)) or tols.shape != (3,)):
+        raise ValueError(message)
+    step_factor = float(tols[2])
+
+    maxiter_int = int(maxiter)
+    if maxiter != maxiter_int or maxiter <= 0:
+        raise ValueError('`maxiter` must be a positive integer.')
+
+    order_int = int(order)
+    if order_int != order or order <= 0:
+        raise ValueError('`order` must be a positive integer.')
+
+    step_direction = xp.asarray(step_direction)
+    initial_step = xp.asarray(initial_step)
+    temp = xp.broadcast_arrays(x, step_direction, initial_step)
+    x, step_direction, initial_step = temp
+
+    message = '`preserve_shape` must be True or False.'
+    if preserve_shape not in {True, False}:
+        raise ValueError(message)
+
+    if callback is not None and not callable(callback):
+        raise ValueError('`callback` must be callable.')
+
+    return (f, x, args, atol, rtol, maxiter_int, order_int, initial_step,
+            step_factor, step_direction, preserve_shape, callback)
+
+
+def derivative(f, x, *, args=(), tolerances=None, maxiter=10,
+               order=8, initial_step=0.5, step_factor=2.0,
+               step_direction=0, preserve_shape=False, callback=None):
+    """Evaluate the derivative of a elementwise, real scalar function numerically.
+
+    For each element of the output of `f`, `derivative` approximates the first
+    derivative of `f` at the corresponding element of `x` using finite difference
+    differentiation.
+
+    This function works elementwise when `x`, `step_direction`, and `args` contain
+    (broadcastable) arrays.
+
+    Parameters
+    ----------
+    f : callable
+        The function whose derivative is desired. The signature must be::
+
+            f(xi: ndarray, *argsi) -> ndarray
+
+        where each element of ``xi`` is a finite real number and ``argsi`` is a tuple,
+        which may contain an arbitrary number of arrays that are broadcastable with
+        ``xi``. `f` must be an elementwise function: each scalar element ``f(xi)[j]``
+        must equal ``f(xi[j])`` for valid indices ``j``. It must not mutate the array
+        ``xi`` or the arrays in ``argsi``.
+    x : float array_like
+        Abscissae at which to evaluate the derivative. Must be broadcastable with
+        `args` and `step_direction`.
+    args : tuple of array_like, optional
+        Additional positional array arguments to be passed to `f`. Arrays
+        must be broadcastable with one another and the arrays of `init`.
+        If the callable for which the root is desired requires arguments that are
+        not broadcastable with `x`, wrap that callable with `f` such that `f`
+        accepts only `x` and broadcastable ``*args``.
+    tolerances : dictionary of floats, optional
+        Absolute and relative tolerances. Valid keys of the dictionary are:
+
+        - ``atol`` - absolute tolerance on the derivative
+        - ``rtol`` - relative tolerance on the derivative
+
+        Iteration will stop when ``res.error < atol + rtol * abs(res.df)``. The default
+        `atol` is the smallest normal number of the appropriate dtype, and
+        the default `rtol` is the square root of the precision of the
+        appropriate dtype.
+    order : int, default: 8
+        The (positive integer) order of the finite difference formula to be
+        used. Odd integers will be rounded up to the next even integer.
+    initial_step : float array_like, default: 0.5
+        The (absolute) initial step size for the finite difference derivative
+        approximation.
+    step_factor : float, default: 2.0
+        The factor by which the step size is *reduced* in each iteration; i.e.
+        the step size in iteration 1 is ``initial_step/step_factor``. If
+        ``step_factor < 1``, subsequent steps will be greater than the initial
+        step; this may be useful if steps smaller than some threshold are
+        undesirable (e.g. due to subtractive cancellation error).
+    maxiter : int, default: 10
+        The maximum number of iterations of the algorithm to perform. See
+        Notes.
+    step_direction : integer array_like
+        An array representing the direction of the finite difference steps (for
+        use when `x` lies near to the boundary of the domain of the function.)
+        Must be broadcastable with `x` and all `args`.
+        Where 0 (default), central differences are used; where negative (e.g.
+        -1), steps are non-positive; and where positive (e.g. 1), all steps are
+        non-negative.
+    preserve_shape : bool, default: False
+        In the following, "arguments of `f`" refers to the array ``xi`` and
+        any arrays within ``argsi``. Let ``shape`` be the broadcasted shape
+        of `x` and all elements of `args` (which is conceptually
+        distinct from ``xi` and ``argsi`` passed into `f`).
+
+        - When ``preserve_shape=False`` (default), `f` must accept arguments
+          of *any* broadcastable shapes.
+
+        - When ``preserve_shape=True``, `f` must accept arguments of shape
+          ``shape`` *or* ``shape + (n,)``, where ``(n,)`` is the number of
+          abscissae at which the function is being evaluated.
+
+        In either case, for each scalar element ``xi[j]`` within ``xi``, the array
+        returned by `f` must include the scalar ``f(xi[j])`` at the same index.
+        Consequently, the shape of the output is always the shape of the input
+        ``xi``.
+
+        See Examples.
+    callback : callable, optional
+        An optional user-supplied function to be called before the first
+        iteration and after each iteration.
+        Called as ``callback(res)``, where ``res`` is a ``_RichResult``
+        similar to that returned by `derivative` (but containing the current
+        iterate's values of all variables). If `callback` raises a
+        ``StopIteration``, the algorithm will terminate immediately and
+        `derivative` will return a result. `callback` must not mutate
+        `res` or its attributes.
+
+    Returns
+    -------
+    res : _RichResult
+        An object similar to an instance of `scipy.optimize.OptimizeResult` with the
+        following attributes. The descriptions are written as though the values will
+        be scalars; however, if `f` returns an array, the outputs will be
+        arrays of the same shape.
+
+        success : bool array
+            ``True`` where the algorithm terminated successfully (status ``0``);
+            ``False`` otherwise.
+        status : int array
+            An integer representing the exit status of the algorithm.
+
+            - ``0`` : The algorithm converged to the specified tolerances.
+            - ``-1`` : The error estimate increased, so iteration was terminated.
+            - ``-2`` : The maximum number of iterations was reached.
+            - ``-3`` : A non-finite value was encountered.
+            - ``-4`` : Iteration was terminated by `callback`.
+            - ``1`` : The algorithm is proceeding normally (in `callback` only).
+
+        df : float array
+            The derivative of `f` at `x`, if the algorithm terminated
+            successfully.
+        error : float array
+            An estimate of the error: the magnitude of the difference between
+            the current estimate of the derivative and the estimate in the
+            previous iteration.
+        nit : int array
+            The number of iterations of the algorithm that were performed.
+        nfev : int array
+            The number of points at which `f` was evaluated.
+        x : float array
+            The value at which the derivative of `f` was evaluated
+            (after broadcasting with `args` and `step_direction`).
+
+    See Also
+    --------
+    jacobian, hessian
+
+    Notes
+    -----
+    The implementation was inspired by jacobi [1]_, numdifftools [2]_, and
+    DERIVEST [3]_, but the implementation follows the theory of Taylor series
+    more straightforwardly (and arguably naively so).
+    In the first iteration, the derivative is estimated using a finite
+    difference formula of order `order` with maximum step size `initial_step`.
+    Each subsequent iteration, the maximum step size is reduced by
+    `step_factor`, and the derivative is estimated again until a termination
+    condition is reached. The error estimate is the magnitude of the difference
+    between the current derivative approximation and that of the previous
+    iteration.
+
+    The stencils of the finite difference formulae are designed such that
+    abscissae are "nested": after `f` is evaluated at ``order + 1``
+    points in the first iteration, `f` is evaluated at only two new points
+    in each subsequent iteration; ``order - 1`` previously evaluated function
+    values required by the finite difference formula are reused, and two
+    function values (evaluations at the points furthest from `x`) are unused.
+
+    Step sizes are absolute. When the step size is small relative to the
+    magnitude of `x`, precision is lost; for example, if `x` is ``1e20``, the
+    default initial step size of ``0.5`` cannot be resolved. Accordingly,
+    consider using larger initial step sizes for large magnitudes of `x`.
+
+    The default tolerances are challenging to satisfy at points where the
+    true derivative is exactly zero. If the derivative may be exactly zero,
+    consider specifying an absolute tolerance (e.g. ``atol=1e-12``) to
+    improve convergence.
+
+    References
+    ----------
+    .. [1] Hans Dembinski (@HDembinski). jacobi.
+           https://github.com/HDembinski/jacobi
+    .. [2] Per A. Brodtkorb and John D'Errico. numdifftools.
+           https://numdifftools.readthedocs.io/en/latest/
+    .. [3] John D'Errico. DERIVEST: Adaptive Robust Numerical Differentiation.
+           https://www.mathworks.com/matlabcentral/fileexchange/13490-adaptive-robust-numerical-differentiation
+    .. [4] Numerical Differentition. Wikipedia.
+           https://en.wikipedia.org/wiki/Numerical_differentiation
+
+    Examples
+    --------
+    Evaluate the derivative of ``np.exp`` at several points ``x``.
+
+    >>> import numpy as np
+    >>> from scipy.differentiate import derivative
+    >>> f = np.exp
+    >>> df = np.exp  # true derivative
+    >>> x = np.linspace(1, 2, 5)
+    >>> res = derivative(f, x)
+    >>> res.df  # approximation of the derivative
+    array([2.71828183, 3.49034296, 4.48168907, 5.75460268, 7.3890561 ])
+    >>> res.error  # estimate of the error
+    array([7.13740178e-12, 9.16600129e-12, 1.17594823e-11, 1.51061386e-11,
+           1.94262384e-11])
+    >>> abs(res.df - df(x))  # true error
+    array([2.53130850e-14, 3.55271368e-14, 5.77315973e-14, 5.59552404e-14,
+           6.92779167e-14])
+
+    Show the convergence of the approximation as the step size is reduced.
+    Each iteration, the step size is reduced by `step_factor`, so for
+    sufficiently small initial step, each iteration reduces the error by a
+    factor of ``1/step_factor**order`` until finite precision arithmetic
+    inhibits further improvement.
+
+    >>> import matplotlib.pyplot as plt
+    >>> iter = list(range(1, 12))  # maximum iterations
+    >>> hfac = 2  # step size reduction per iteration
+    >>> hdir = [-1, 0, 1]  # compare left-, central-, and right- steps
+    >>> order = 4  # order of differentiation formula
+    >>> x = 1
+    >>> ref = df(x)
+    >>> errors = []  # true error
+    >>> for i in iter:
+    ...     res = derivative(f, x, maxiter=i, step_factor=hfac,
+    ...                      step_direction=hdir, order=order,
+    ...                      # prevent early termination
+    ...                      tolerances=dict(atol=0, rtol=0))
+    ...     errors.append(abs(res.df - ref))
+    >>> errors = np.array(errors)
+    >>> plt.semilogy(iter, errors[:, 0], label='left differences')
+    >>> plt.semilogy(iter, errors[:, 1], label='central differences')
+    >>> plt.semilogy(iter, errors[:, 2], label='right differences')
+    >>> plt.xlabel('iteration')
+    >>> plt.ylabel('error')
+    >>> plt.legend()
+    >>> plt.show()
+    >>> (errors[1, 1] / errors[0, 1], 1 / hfac**order)
+    (0.06215223140159822, 0.0625)
+
+    The implementation is vectorized over `x`, `step_direction`, and `args`.
+    The function is evaluated once before the first iteration to perform input
+    validation and standardization, and once per iteration thereafter.
+
+    >>> def f(x, p):
+    ...     f.nit += 1
+    ...     return x**p
+    >>> f.nit = 0
+    >>> def df(x, p):
+    ...     return p*x**(p-1)
+    >>> x = np.arange(1, 5)
+    >>> p = np.arange(1, 6).reshape((-1, 1))
+    >>> hdir = np.arange(-1, 2).reshape((-1, 1, 1))
+    >>> res = derivative(f, x, args=(p,), step_direction=hdir, maxiter=1)
+    >>> np.allclose(res.df, df(x, p))
+    True
+    >>> res.df.shape
+    (3, 5, 4)
+    >>> f.nit
+    2
+
+    By default, `preserve_shape` is False, and therefore the callable
+    `f` may be called with arrays of any broadcastable shapes.
+    For example:
+
+    >>> shapes = []
+    >>> def f(x, c):
+    ...    shape = np.broadcast_shapes(x.shape, c.shape)
+    ...    shapes.append(shape)
+    ...    return np.sin(c*x)
+    >>>
+    >>> c = [1, 5, 10, 20]
+    >>> res = derivative(f, 0, args=(c,))
+    >>> shapes
+    [(4,), (4, 8), (4, 2), (3, 2), (2, 2), (1, 2)]
+
+    To understand where these shapes are coming from - and to better
+    understand how `derivative` computes accurate results - note that
+    higher values of ``c`` correspond with higher frequency sinusoids.
+    The higher frequency sinusoids make the function's derivative change
+    faster, so more function evaluations are required to achieve the target
+    accuracy:
+
+    >>> res.nfev
+    array([11, 13, 15, 17], dtype=int32)
+
+    The initial ``shape``, ``(4,)``, corresponds with evaluating the
+    function at a single abscissa and all four frequencies; this is used
+    for input validation and to determine the size and dtype of the arrays
+    that store results. The next shape corresponds with evaluating the
+    function at an initial grid of abscissae and all four frequencies.
+    Successive calls to the function evaluate the function at two more
+    abscissae, increasing the effective order of the approximation by two.
+    However, in later function evaluations, the function is evaluated at
+    fewer frequencies because the corresponding derivative has already
+    converged to the required tolerance. This saves function evaluations to
+    improve performance, but it requires the function to accept arguments of
+    any shape.
+
+    "Vector-valued" functions are unlikely to satisfy this requirement.
+    For example, consider
+
+    >>> def f(x):
+    ...    return [x, np.sin(3*x), x+np.sin(10*x), np.sin(20*x)*(x-1)**2]
+
+    This integrand is not compatible with `derivative` as written; for instance,
+    the shape of the output will not be the same as the shape of ``x``. Such a
+    function *could* be converted to a compatible form with the introduction of
+    additional parameters, but this would be inconvenient. In such cases,
+    a simpler solution would be to use `preserve_shape`.
+
+    >>> shapes = []
+    >>> def f(x):
+    ...     shapes.append(x.shape)
+    ...     x0, x1, x2, x3 = x
+    ...     return [x0, np.sin(3*x1), x2+np.sin(10*x2), np.sin(20*x3)*(x3-1)**2]
+    >>>
+    >>> x = np.zeros(4)
+    >>> res = derivative(f, x, preserve_shape=True)
+    >>> shapes
+    [(4,), (4, 8), (4, 2), (4, 2), (4, 2), (4, 2)]
+
+    Here, the shape of ``x`` is ``(4,)``. With ``preserve_shape=True``, the
+    function may be called with argument ``x`` of shape ``(4,)`` or ``(4, n)``,
+    and this is what we observe.
+
+    """
+    # TODO (followup):
+    #  - investigate behavior at saddle points
+    #  - multivariate functions?
+    #  - relative steps?
+    #  - show example of `np.vectorize`
+
+    res = _derivative_iv(f, x, args, tolerances, maxiter, order, initial_step,
+                            step_factor, step_direction, preserve_shape, callback)
+    (func, x, args, atol, rtol, maxiter, order,
+     h0, fac, hdir, preserve_shape, callback) = res
+
+    # Initialization
+    # Since f(x) (no step) is not needed for central differences, it may be
+    # possible to eliminate this function evaluation. However, it's useful for
+    # input validation and standardization, and everything else is designed to
+    # reduce function calls, so let's keep it simple.
+    temp = eim._initialize(func, (x,), args, preserve_shape=preserve_shape)
+    func, xs, fs, args, shape, dtype, xp = temp
+
+    finfo = xp.finfo(dtype)
+    atol = finfo.smallest_normal if atol is None else atol
+    rtol = finfo.eps**0.5 if rtol is None else rtol  # keep same as `hessian`
+
+    x, f = xs[0], fs[0]
+    df = xp.full_like(f, xp.nan)
+
+    # Ideally we'd broadcast the shape of `hdir` in `_elementwise_algo_init`, but
+    # it's simpler to do it here than to generalize `_elementwise_algo_init` further.
+    # `hdir` and `x` are already broadcasted in `_derivative_iv`, so we know
+    # that `hdir` can be broadcasted to the final shape. Same with `h0`.
+    hdir = xp.broadcast_to(hdir, shape)
+    hdir = xp.reshape(hdir, (-1,))
+    hdir = xp.astype(xp_sign(hdir), dtype)
+    h0 = xp.broadcast_to(h0, shape)
+    h0 = xp.reshape(h0, (-1,))
+    h0 = xp.astype(h0, dtype)
+    h0[h0 <= 0] = xp.asarray(xp.nan, dtype=dtype)
+
+    status = xp.full_like(x, eim._EINPROGRESS, dtype=xp.int32)  # in progress
+    nit, nfev = 0, 1  # one function evaluations performed above
+    # Boolean indices of left, central, right, and (all) one-sided steps
+    il = hdir < 0
+    ic = hdir == 0
+    ir = hdir > 0
+    io = il | ir
+
+    # Most of these attributes are reasonably obvious, but:
+    # - `fs` holds all the function values of all active `x`. The zeroth
+    #   axis corresponds with active points `x`, the first axis corresponds
+    #   with the different steps (in the order described in
+    #   `_derivative_weights`).
+    # - `terms` (which could probably use a better name) is half the `order`,
+    #   which is always even.
+    work = _RichResult(x=x, df=df, fs=f[:, xp.newaxis], error=xp.nan, h=h0,
+                       df_last=xp.nan, error_last=xp.nan, fac=fac,
+                       atol=atol, rtol=rtol, nit=nit, nfev=nfev,
+                       status=status, dtype=dtype, terms=(order+1)//2,
+                       hdir=hdir, il=il, ic=ic, ir=ir, io=io,
+                       # Store the weights in an object so they can't get compressed
+                       # Using RichResult to allow dot notation, but a dict would work
+                       diff_state=_RichResult(central=[], right=[], fac=None))
+
+    # This is the correspondence between terms in the `work` object and the
+    # final result. In this case, the mapping is trivial. Note that `success`
+    # is prepended automatically.
+    res_work_pairs = [('status', 'status'), ('df', 'df'), ('error', 'error'),
+                      ('nit', 'nit'), ('nfev', 'nfev'), ('x', 'x')]
+
+    def pre_func_eval(work):
+        """Determine the abscissae at which the function needs to be evaluated.
+
+        See `_derivative_weights` for a description of the stencil (pattern
+        of the abscissae).
+
+        In the first iteration, there is only one stored function value in
+        `work.fs`, `f(x)`, so we need to evaluate at `order` new points. In
+        subsequent iterations, we evaluate at two new points. Note that
+        `work.x` is always flattened into a 1D array after broadcasting with
+        all `args`, so we add a new axis at the end and evaluate all point
+        in one call to the function.
+
+        For improvement:
+        - Consider measuring the step size actually taken, since ``(x + h) - x``
+          is not identically equal to `h` with floating point arithmetic.
+        - Adjust the step size automatically if `x` is too big to resolve the
+          step.
+        - We could probably save some work if there are no central difference
+          steps or no one-sided steps.
+        """
+        n = work.terms  # half the order
+        h = work.h[:, xp.newaxis]  # step size
+        c = work.fac  # step reduction factor
+        d = c**0.5  # square root of step reduction factor (one-sided stencil)
+        # Note - no need to be careful about dtypes until we allocate `x_eval`
+
+        if work.nit == 0:
+            hc = h / c**xp.arange(n, dtype=work.dtype)
+            hc = xp.concat((-xp.flip(hc, axis=-1), hc), axis=-1)
+        else:
+            hc = xp.concat((-h, h), axis=-1) / c**(n-1)
+
+        if work.nit == 0:
+            hr = h / d**xp.arange(2*n, dtype=work.dtype)
+        else:
+            hr = xp.concat((h, h/d), axis=-1) / c**(n-1)
+
+        n_new = 2*n if work.nit == 0 else 2  # number of new abscissae
+        x_eval = xp.zeros((work.hdir.shape[0], n_new), dtype=work.dtype)
+        il, ic, ir = work.il, work.ic, work.ir
+        x_eval[ir] = work.x[ir][:, xp.newaxis] + hr[ir]
+        x_eval[ic] = work.x[ic][:, xp.newaxis] + hc[ic]
+        x_eval[il] = work.x[il][:, xp.newaxis] - hr[il]
+        return x_eval
+
+    def post_func_eval(x, f, work):
+        """ Estimate the derivative and error from the function evaluations
+
+        As in `pre_func_eval`: in the first iteration, there is only one stored
+        function value in `work.fs`, `f(x)`, so we need to add the `order` new
+        points. In subsequent iterations, we add two new points. The tricky
+        part is getting the order to match that of the weights, which is
+        described in `_derivative_weights`.
+
+        For improvement:
+        - Change the order of the weights (and steps in `pre_func_eval`) to
+          simplify `work_fc` concatenation and eliminate `fc` concatenation.
+        - It would be simple to do one-step Richardson extrapolation with `df`
+          and `df_last` to increase the order of the estimate and/or improve
+          the error estimate.
+        - Process the function evaluations in a more numerically favorable
+          way. For instance, combining the pairs of central difference evals
+          into a second-order approximation and using Richardson extrapolation
+          to produce a higher order approximation seemed to retain accuracy up
+          to very high order.
+        - Alternatively, we could use `polyfit` like Jacobi. An advantage of
+          fitting polynomial to more points than necessary is improved noise
+          tolerance.
+        """
+        n = work.terms
+        n_new = n if work.nit == 0 else 1
+        il, ic, io = work.il, work.ic, work.io
+
+        # Central difference
+        # `work_fc` is *all* the points at which the function has been evaluated
+        # `fc` is the points we're using *this iteration* to produce the estimate
+        work_fc = (f[ic][:, :n_new], work.fs[ic], f[ic][:, -n_new:])
+        work_fc = xp.concat(work_fc, axis=-1)
+        if work.nit == 0:
+            fc = work_fc
+        else:
+            fc = (work_fc[:, :n], work_fc[:, n:n+1], work_fc[:, -n:])
+            fc = xp.concat(fc, axis=-1)
+
+        # One-sided difference
+        work_fo = xp.concat((work.fs[io], f[io]), axis=-1)
+        if work.nit == 0:
+            fo = work_fo
+        else:
+            fo = xp.concat((work_fo[:, 0:1], work_fo[:, -2*n:]), axis=-1)
+
+        work.fs = xp.zeros((ic.shape[0], work.fs.shape[-1] + 2*n_new), dtype=work.dtype)
+        work.fs[ic] = work_fc
+        work.fs[io] = work_fo
+
+        wc, wo = _derivative_weights(work, n, xp)
+        work.df_last = xp.asarray(work.df, copy=True)
+        work.df[ic] = fc @ wc / work.h[ic]
+        work.df[io] = fo @ wo / work.h[io]
+        work.df[il] *= -1
+
+        work.h /= work.fac
+        work.error_last = work.error
+        # Simple error estimate - the difference in derivative estimates between
+        # this iteration and the last. This is typically conservative because if
+        # convergence has begin, the true error is much closer to the difference
+        # between the current estimate and the *next* error estimate. However,
+        # we could use Richarson extrapolation to produce an error estimate that
+        # is one order higher, and take the difference between that and
+        # `work.df` (which would just be constant factor that depends on `fac`.)
+        work.error = xp.abs(work.df - work.df_last)
+
+    def check_termination(work):
+        """Terminate due to convergence, non-finite values, or error increase"""
+        stop = xp.astype(xp.zeros_like(work.df), xp.bool)
+
+        i = work.error < work.atol + work.rtol*abs(work.df)
+        work.status[i] = eim._ECONVERGED
+        stop[i] = True
+
+        if work.nit > 0:
+            i = ~((xp.isfinite(work.x) & xp.isfinite(work.df)) | stop)
+            work.df[i], work.status[i] = xp.nan, eim._EVALUEERR
+            stop[i] = True
+
+        # With infinite precision, there is a step size below which
+        # all smaller step sizes will reduce the error. But in floating point
+        # arithmetic, catastrophic cancellation will begin to cause the error
+        # to increase again. This heuristic tries to avoid step sizes that are
+        # too small. There may be more theoretically sound approaches for
+        # detecting a step size that minimizes the total error, but this
+        # heuristic seems simple and effective.
+        i = (work.error > work.error_last*10) & ~stop
+        work.status[i] = _EERRORINCREASE
+        stop[i] = True
+
+        return stop
+
+    def post_termination_check(work):
+        return
+
+    def customize_result(res, shape):
+        return shape
+
+    return eim._loop(work, callback, shape, maxiter, func, args, dtype,
+                     pre_func_eval, post_func_eval, check_termination,
+                     post_termination_check, customize_result, res_work_pairs,
+                     xp, preserve_shape)
+
+
+def _derivative_weights(work, n, xp):
+    # This produces the weights of the finite difference formula for a given
+    # stencil. In experiments, use of a second-order central difference formula
+    # with Richardson extrapolation was more accurate numerically, but it was
+    # more complicated, and it would have become even more complicated when
+    # adding support for one-sided differences. However, now that all the
+    # function evaluation values are stored, they can be processed in whatever
+    # way is desired to produce the derivative estimate. We leave alternative
+    # approaches to future work. To be more self-contained, here is the theory
+    # for deriving the weights below.
+    #
+    # Recall that the Taylor expansion of a univariate, scalar-values function
+    # about a point `x` may be expressed as:
+    #      f(x + h)  =     f(x) + f'(x)*h + f''(x)/2!*h**2  + O(h**3)
+    # Suppose we evaluate f(x), f(x+h), and f(x-h).  We have:
+    #      f(x)      =     f(x)
+    #      f(x + h)  =     f(x) + f'(x)*h + f''(x)/2!*h**2  + O(h**3)
+    #      f(x - h)  =     f(x) - f'(x)*h + f''(x)/2!*h**2  + O(h**3)
+    # We can solve for weights `wi` such that:
+    #   w1*f(x)      = w1*(f(x))
+    # + w2*f(x + h)  = w2*(f(x) + f'(x)*h + f''(x)/2!*h**2) + O(h**3)
+    # + w3*f(x - h)  = w3*(f(x) - f'(x)*h + f''(x)/2!*h**2) + O(h**3)
+    #                =     0    + f'(x)*h + 0               + O(h**3)
+    # Then
+    #     f'(x) ~ (w1*f(x) + w2*f(x+h) + w3*f(x-h))/h
+    # is a finite difference derivative approximation with error O(h**2),
+    # and so it is said to be a "second-order" approximation. Under certain
+    # conditions (e.g. well-behaved function, `h` sufficiently small), the
+    # error in the approximation will decrease with h**2; that is, if `h` is
+    # reduced by a factor of 2, the error is reduced by a factor of 4.
+    #
+    # By default, we use eighth-order formulae. Our central-difference formula
+    # uses abscissae:
+    #   x-h/c**3, x-h/c**2, x-h/c, x-h, x, x+h, x+h/c, x+h/c**2, x+h/c**3
+    # where `c` is the step factor. (Typically, the step factor is greater than
+    # one, so the outermost points - as written above - are actually closest to
+    # `x`.) This "stencil" is chosen so that each iteration, the step can be
+    # reduced by the factor `c`, and most of the function evaluations can be
+    # reused with the new step size. For example, in the next iteration, we
+    # will have:
+    #   x-h/c**4, x-h/c**3, x-h/c**2, x-h/c, x, x+h/c, x+h/c**2, x+h/c**3, x+h/c**4
+    # We do not reuse `x-h` and `x+h` for the new derivative estimate.
+    # While this would increase the order of the formula and thus the
+    # theoretical convergence rate, it is also less stable numerically.
+    # (As noted above, there are other ways of processing the values that are
+    # more stable. Thus, even now we store `f(x-h)` and `f(x+h)` in `work.fs`
+    # to simplify future development of this sort of improvement.)
+    #
+    # The (right) one-sided formula is produced similarly using abscissae
+    #   x, x+h, x+h/d, x+h/d**2, ..., x+h/d**6, x+h/d**7, x+h/d**7
+    # where `d` is the square root of `c`. (The left one-sided formula simply
+    # uses -h.) When the step size is reduced by factor `c = d**2`, we have
+    # abscissae:
+    #   x, x+h/d**2, x+h/d**3..., x+h/d**8, x+h/d**9, x+h/d**9
+    # `d` is chosen as the square root of `c` so that the rate of the step-size
+    # reduction is the same per iteration as in the central difference case.
+    # Note that because the central difference formulas are inherently of even
+    # order, for simplicity, we use only even-order formulas for one-sided
+    # differences, too.
+
+    # It's possible for the user to specify `fac` in, say, double precision but
+    # `x` and `args` in single precision. `fac` gets converted to single
+    # precision, but we should always use double precision for the intermediate
+    # calculations here to avoid additional error in the weights.
+    fac = float(work.fac)
+
+    # Note that if the user switches back to floating point precision with
+    # `x` and `args`, then `fac` will not necessarily equal the (lower
+    # precision) cached `_derivative_weights.fac`, and the weights will
+    # need to be recalculated. This could be fixed, but it's late, and of
+    # low consequence.
+
+    diff_state = work.diff_state
+    if fac != diff_state.fac:
+        diff_state.central = []
+        diff_state.right = []
+        diff_state.fac = fac
+
+    if len(diff_state.central) != 2*n + 1:
+        # Central difference weights. Consider refactoring this; it could
+        # probably be more compact.
+        # Note: Using NumPy here is OK; we convert to xp-type at the end
+        i = np.arange(-n, n + 1)
+        p = np.abs(i) - 1.  # center point has power `p` -1, but sign `s` is 0
+        s = np.sign(i)
+
+        h = s / fac ** p
+        A = np.vander(h, increasing=True).T
+        b = np.zeros(2*n + 1)
+        b[1] = 1
+        weights = np.linalg.solve(A, b)
+
+        # Enforce identities to improve accuracy
+        weights[n] = 0
+        for i in range(n):
+            weights[-i-1] = -weights[i]
+
+        # Cache the weights. We only need to calculate them once unless
+        # the step factor changes.
+        diff_state.central = weights
+
+        # One-sided difference weights. The left one-sided weights (with
+        # negative steps) are simply the negative of the right one-sided
+        # weights, so no need to compute them separately.
+        i = np.arange(2*n + 1)
+        p = i - 1.
+        s = np.sign(i)
+
+        h = s / np.sqrt(fac) ** p
+        A = np.vander(h, increasing=True).T
+        b = np.zeros(2 * n + 1)
+        b[1] = 1
+        weights = np.linalg.solve(A, b)
+
+        diff_state.right = weights
+
+    return (xp.asarray(diff_state.central, dtype=work.dtype),
+            xp.asarray(diff_state.right, dtype=work.dtype))
+
+
+def jacobian(f, x, *, tolerances=None, maxiter=10, order=8, initial_step=0.5,
+             step_factor=2.0, step_direction=0):
+    r"""Evaluate the Jacobian of a function numerically.
+
+    Parameters
+    ----------
+    f : callable
+        The function whose Jacobian is desired. The signature must be::
+
+            f(xi: ndarray) -> ndarray
+
+        where each element of ``xi`` is a finite real. If the function to be
+        differentiated accepts additional arguments, wrap it (e.g. using
+        `functools.partial` or ``lambda``) and pass the wrapped callable
+        into `jacobian`. `f` must not mutate the array ``xi``. See Notes
+        regarding vectorization and the dimensionality of the input and output.
+    x : float array_like
+        Points at which to evaluate the Jacobian. Must have at least one dimension.
+        See Notes regarding the dimensionality and vectorization.
+    tolerances : dictionary of floats, optional
+        Absolute and relative tolerances. Valid keys of the dictionary are:
+
+        - ``atol`` - absolute tolerance on the derivative
+        - ``rtol`` - relative tolerance on the derivative
+
+        Iteration will stop when ``res.error < atol + rtol * abs(res.df)``. The default
+        `atol` is the smallest normal number of the appropriate dtype, and
+        the default `rtol` is the square root of the precision of the
+        appropriate dtype.
+    maxiter : int, default: 10
+        The maximum number of iterations of the algorithm to perform. See
+        Notes.
+    order : int, default: 8
+        The (positive integer) order of the finite difference formula to be
+        used. Odd integers will be rounded up to the next even integer.
+    initial_step : float array_like, default: 0.5
+        The (absolute) initial step size for the finite difference derivative
+        approximation. Must be broadcastable with `x` and `step_direction`.
+    step_factor : float, default: 2.0
+        The factor by which the step size is *reduced* in each iteration; i.e.
+        the step size in iteration 1 is ``initial_step/step_factor``. If
+        ``step_factor < 1``, subsequent steps will be greater than the initial
+        step; this may be useful if steps smaller than some threshold are
+        undesirable (e.g. due to subtractive cancellation error).
+    step_direction : integer array_like
+        An array representing the direction of the finite difference steps (e.g.
+        for use when `x` lies near to the boundary of the domain of the function.)
+        Must be broadcastable with `x` and `initial_step`.
+        Where 0 (default), central differences are used; where negative (e.g.
+        -1), steps are non-positive; and where positive (e.g. 1), all steps are
+        non-negative.
+
+    Returns
+    -------
+    res : _RichResult
+        An object similar to an instance of `scipy.optimize.OptimizeResult` with the
+        following attributes. The descriptions are written as though the values will
+        be scalars; however, if `f` returns an array, the outputs will be
+        arrays of the same shape.
+
+        success : bool array
+            ``True`` where the algorithm terminated successfully (status ``0``);
+            ``False`` otherwise.
+        status : int array
+            An integer representing the exit status of the algorithm.
+
+            - ``0`` : The algorithm converged to the specified tolerances.
+            - ``-1`` : The error estimate increased, so iteration was terminated.
+            - ``-2`` : The maximum number of iterations was reached.
+            - ``-3`` : A non-finite value was encountered.
+
+        df : float array
+            The Jacobian of `f` at `x`, if the algorithm terminated
+            successfully.
+        error : float array
+            An estimate of the error: the magnitude of the difference between
+            the current estimate of the Jacobian and the estimate in the
+            previous iteration.
+        nit : int array
+            The number of iterations of the algorithm that were performed.
+        nfev : int array
+            The number of points at which `f` was evaluated.
+
+        Each element of an attribute is associated with the corresponding
+        element of `df`. For instance, element ``i`` of `nfev` is the
+        number of points at which `f` was evaluated for the sake of
+        computing element ``i`` of `df`.
+
+    See Also
+    --------
+    derivative, hessian
+
+    Notes
+    -----
+    Suppose we wish to evaluate the Jacobian of a function
+    :math:`f: \mathbf{R}^m \rightarrow \mathbf{R}^n`. Assign to variables
+    ``m`` and ``n`` the positive integer values of :math:`m` and :math:`n`,
+    respectively, and let ``...`` represent an arbitrary tuple of integers.
+    If we wish to evaluate the Jacobian at a single point, then:
+
+    - argument `x` must be an array of shape ``(m,)``
+    - argument `f` must be vectorized to accept an array of shape ``(m, ...)``.
+      The first axis represents the :math:`m` inputs of :math:`f`; the remainder
+      are for evaluating the function at multiple points in a single call.
+    - argument `f` must return an array of shape ``(n, ...)``. The first
+      axis represents the :math:`n` outputs of :math:`f`; the remainder
+      are for the result of evaluating the function at multiple points.
+    - attribute ``df`` of the result object will be an array of shape ``(n, m)``,
+      the Jacobian.
+
+    This function is also vectorized in the sense that the Jacobian can be
+    evaluated at ``k`` points in a single call. In this case, `x` would be an
+    array of shape ``(m, k)``, `f` would accept an array of shape
+    ``(m, k, ...)`` and return an array of shape ``(n, k, ...)``, and the ``df``
+    attribute of the result would have shape ``(n, m, k)``.
+
+    Suppose the desired callable ``f_not_vectorized`` is not vectorized; it can
+    only accept an array of shape ``(m,)``. A simple solution to satisfy the required
+    interface is to wrap ``f_not_vectorized`` as follows::
+
+        def f(x):
+            return np.apply_along_axis(f_not_vectorized, axis=0, arr=x)
+
+    Alternatively, suppose the desired callable ``f_vec_q`` is vectorized, but
+    only for 2-D arrays of shape ``(m, q)``. To satisfy the required interface,
+    consider::
+
+        def f(x):
+            m, batch = x.shape[0], x.shape[1:]  # x.shape is (m, ...)
+            x = np.reshape(x, (m, -1))  # `-1` is short for q = prod(batch)
+            res = f_vec_q(x)  # pass shape (m, q) to function
+            n = res.shape[0]
+            return np.reshape(res, (n,) + batch)  # return shape (n, ...)
+
+    Then pass the wrapped callable ``f`` as the first argument of `jacobian`.
+
+    References
+    ----------
+    .. [1] Jacobian matrix and determinant, *Wikipedia*,
+           https://en.wikipedia.org/wiki/Jacobian_matrix_and_determinant
+
+    Examples
+    --------
+    The Rosenbrock function maps from :math:`\mathbf{R}^m \rightarrow \mathbf{R}`;
+    the SciPy implementation `scipy.optimize.rosen` is vectorized to accept an
+    array of shape ``(m, p)`` and return an array of shape ``p``. Suppose we wish
+    to evaluate the Jacobian (AKA the gradient because the function returns a scalar)
+    at ``[0.5, 0.5, 0.5]``.
+
+    >>> import numpy as np
+    >>> from scipy.differentiate import jacobian
+    >>> from scipy.optimize import rosen, rosen_der
+    >>> m = 3
+    >>> x = np.full(m, 0.5)
+    >>> res = jacobian(rosen, x)
+    >>> ref = rosen_der(x)  # reference value of the gradient
+    >>> res.df, ref
+    (array([-51.,  -1.,  50.]), array([-51.,  -1.,  50.]))
+
+    As an example of a function with multiple outputs, consider Example 4
+    from [1]_.
+
+    >>> def f(x):
+    ...     x1, x2, x3 = x
+    ...     return [x1, 5*x3, 4*x2**2 - 2*x3, x3*np.sin(x1)]
+
+    The true Jacobian is given by:
+
+    >>> def df(x):
+    ...         x1, x2, x3 = x
+    ...         one = np.ones_like(x1)
+    ...         return [[one, 0*one, 0*one],
+    ...                 [0*one, 0*one, 5*one],
+    ...                 [0*one, 8*x2, -2*one],
+    ...                 [x3*np.cos(x1), 0*one, np.sin(x1)]]
+
+    Evaluate the Jacobian at an arbitrary point.
+
+    >>> rng = np.random.default_rng(389252938452)
+    >>> x = rng.random(size=3)
+    >>> res = jacobian(f, x)
+    >>> ref = df(x)
+    >>> res.df.shape == (4, 3)
+    True
+    >>> np.allclose(res.df, ref)
+    True
+
+    Evaluate the Jacobian at 10 arbitrary points in a single call.
+
+    >>> x = rng.random(size=(3, 10))
+    >>> res = jacobian(f, x)
+    >>> ref = df(x)
+    >>> res.df.shape == (4, 3, 10)
+    True
+    >>> np.allclose(res.df, ref)
+    True
+
+    """
+    xp = array_namespace(x)
+    x = xp.asarray(x)
+    int_dtype = xp.isdtype(x.dtype, 'integral')
+    x0 = xp.asarray(x, dtype=xp.asarray(1.0).dtype) if int_dtype else x
+
+    if x0.ndim < 1:
+        message = "Argument `x` must be at least 1-D."
+        raise ValueError(message)
+
+    m = x0.shape[0]
+    i = xp.arange(m)
+
+    def wrapped(x):
+        p = () if x.ndim == x0.ndim else (x.shape[-1],)  # number of abscissae
+
+        new_shape = (m, m) + x0.shape[1:] + p
+        xph = xp.expand_dims(x0, axis=1)
+        if x.ndim != x0.ndim:
+            xph = xp.expand_dims(xph, axis=-1)
+        xph = xp_copy(xp.broadcast_to(xph, new_shape), xp=xp)
+        xph[i, i] = x
+        return f(xph)
+
+    res = derivative(wrapped, x, tolerances=tolerances,
+                     maxiter=maxiter, order=order, initial_step=initial_step,
+                     step_factor=step_factor, preserve_shape=True,
+                     step_direction=step_direction)
+
+    del res.x  # the user knows `x`, and the way it gets broadcasted is meaningless here
+    return res
+
+
+def hessian(f, x, *, tolerances=None, maxiter=10,
+            order=8, initial_step=0.5, step_factor=2.0):
+    r"""Evaluate the Hessian of a function numerically.
+
+    Parameters
+    ----------
+    f : callable
+        The function whose Hessian is desired. The signature must be::
+
+            f(xi: ndarray) -> ndarray
+
+        where each element of ``xi`` is a finite real. If the function to be
+        differentiated accepts additional arguments, wrap it (e.g. using
+        `functools.partial` or ``lambda``) and pass the wrapped callable
+        into `hessian`. `f` must not mutate the array ``xi``. See Notes
+        regarding vectorization and the dimensionality of the input and output.
+    x : float array_like
+        Points at which to evaluate the Hessian. Must have at least one dimension.
+        See Notes regarding the dimensionality and vectorization.
+    tolerances : dictionary of floats, optional
+        Absolute and relative tolerances. Valid keys of the dictionary are:
+
+        - ``atol`` - absolute tolerance on the derivative
+        - ``rtol`` - relative tolerance on the derivative
+
+        Iteration will stop when ``res.error < atol + rtol * abs(res.df)``. The default
+        `atol` is the smallest normal number of the appropriate dtype, and
+        the default `rtol` is the square root of the precision of the
+        appropriate dtype.
+    order : int, default: 8
+        The (positive integer) order of the finite difference formula to be
+        used. Odd integers will be rounded up to the next even integer.
+    initial_step : float, default: 0.5
+        The (absolute) initial step size for the finite difference derivative
+        approximation.
+    step_factor : float, default: 2.0
+        The factor by which the step size is *reduced* in each iteration; i.e.
+        the step size in iteration 1 is ``initial_step/step_factor``. If
+        ``step_factor < 1``, subsequent steps will be greater than the initial
+        step; this may be useful if steps smaller than some threshold are
+        undesirable (e.g. due to subtractive cancellation error).
+    maxiter : int, default: 10
+        The maximum number of iterations of the algorithm to perform. See
+        Notes.
+
+    Returns
+    -------
+    res : _RichResult
+        An object similar to an instance of `scipy.optimize.OptimizeResult` with the
+        following attributes. The descriptions are written as though the values will
+        be scalars; however, if `f` returns an array, the outputs will be
+        arrays of the same shape.
+
+        success : bool array
+            ``True`` where the algorithm terminated successfully (status ``0``);
+            ``False`` otherwise.
+        status : int array
+            An integer representing the exit status of the algorithm.
+
+            - ``0`` : The algorithm converged to the specified tolerances.
+            - ``-1`` : The error estimate increased, so iteration was terminated.
+            - ``-2`` : The maximum number of iterations was reached.
+            - ``-3`` : A non-finite value was encountered.
+
+        ddf : float array
+            The Hessian of `f` at `x`, if the algorithm terminated
+            successfully.
+        error : float array
+            An estimate of the error: the magnitude of the difference between
+            the current estimate of the Hessian and the estimate in the
+            previous iteration.
+        nfev : int array
+            The number of points at which `f` was evaluated.
+
+        Each element of an attribute is associated with the corresponding
+        element of `ddf`. For instance, element ``[i, j]`` of `nfev` is the
+        number of points at which `f` was evaluated for the sake of
+        computing element ``[i, j]`` of `ddf`.
+
+    See Also
+    --------
+    derivative, jacobian
+
+    Notes
+    -----
+    Suppose we wish to evaluate the Hessian of a function
+    :math:`f: \mathbf{R}^m \rightarrow \mathbf{R}`, and we assign to variable
+    ``m`` the positive integer value of :math:`m`. If we wish to evaluate
+    the Hessian at a single point, then:
+
+    - argument `x` must be an array of shape ``(m,)``
+    - argument `f` must be vectorized to accept an array of shape
+      ``(m, ...)``. The first axis represents the :math:`m` inputs of
+      :math:`f`; the remaining axes indicated by ellipses are for evaluating
+      the function at several abscissae in a single call.
+    - argument `f` must return an array of shape ``(...)``.
+    - attribute ``dff`` of the result object will be an array of shape ``(m, m)``,
+      the Hessian.
+
+    This function is also vectorized in the sense that the Hessian can be
+    evaluated at ``k`` points in a single call. In this case, `x` would be an
+    array of shape ``(m, k)``, `f` would accept an array of shape
+    ``(m, ...)`` and return an array of shape ``(...)``, and the ``ddf``
+    attribute of the result would have shape ``(m, m, k)``. Note that the
+    axis associated with the ``k`` points is included within the axes
+    denoted by ``(...)``.
+
+    Currently, `hessian` is implemented by nesting calls to `jacobian`.
+    All options passed to `hessian` are used for both the inner and outer
+    calls with one exception: the `rtol` used in the inner `jacobian` call
+    is tightened by a factor of 100 with the expectation that the inner
+    error can be ignored. A consequence is that `rtol` should not be set
+    less than 100 times the precision of the dtype of `x`; a warning is
+    emitted otherwise.
+
+    References
+    ----------
+    .. [1] Hessian matrix, *Wikipedia*,
+           https://en.wikipedia.org/wiki/Hessian_matrix
+
+    Examples
+    --------
+    The Rosenbrock function maps from :math:`\mathbf{R}^m \rightarrow \mathbf{R}`;
+    the SciPy implementation `scipy.optimize.rosen` is vectorized to accept an
+    array of shape ``(m, ...)`` and return an array of shape ``...``. Suppose we
+    wish to evaluate the Hessian at ``[0.5, 0.5, 0.5]``.
+
+    >>> import numpy as np
+    >>> from scipy.differentiate import hessian
+    >>> from scipy.optimize import rosen, rosen_hess
+    >>> m = 3
+    >>> x = np.full(m, 0.5)
+    >>> res = hessian(rosen, x)
+    >>> ref = rosen_hess(x)  # reference value of the Hessian
+    >>> np.allclose(res.ddf, ref)
+    True
+
+    `hessian` is vectorized to evaluate the Hessian at multiple points
+    in a single call.
+
+    >>> rng = np.random.default_rng(4589245925010)
+    >>> x = rng.random((m, 10))
+    >>> res = hessian(rosen, x)
+    >>> ref = [rosen_hess(xi) for xi in x.T]
+    >>> ref = np.moveaxis(ref, 0, -1)
+    >>> np.allclose(res.ddf, ref)
+    True
+
+    """
+    # todo:
+    # - add ability to vectorize over additional parameters (*args?)
+    # - error estimate stack with inner jacobian (or use legit 2D stencil)
+
+    kwargs = dict(maxiter=maxiter, order=order, initial_step=initial_step,
+                  step_factor=step_factor)
+    tolerances = {} if tolerances is None else tolerances
+    atol = tolerances.get('atol', None)
+    rtol = tolerances.get('rtol', None)
+
+    xp = array_namespace(x)
+    x = xp.asarray(x)
+    dtype = x.dtype if not xp.isdtype(x.dtype, 'integral') else xp.asarray(1.).dtype
+    finfo = xp.finfo(dtype)
+    rtol = finfo.eps**0.5 if rtol is None else rtol  # keep same as `derivative`
+
+    # tighten the inner tolerance to make the inner error negligible
+    rtol_min = finfo.eps * 100
+    message = (f"The specified `{rtol=}`, but error estimates are likely to be "
+               f"unreliable when `rtol < {rtol_min}`.")
+    if 0 < rtol < rtol_min:  # rtol <= 0 is an error
+        warnings.warn(message, RuntimeWarning, stacklevel=2)
+        rtol = rtol_min
+
+    def df(x):
+        tolerances = dict(rtol=rtol/100, atol=atol)
+        temp = jacobian(f, x, tolerances=tolerances, **kwargs)
+        nfev.append(temp.nfev if len(nfev) == 0 else temp.nfev.sum(axis=-1))
+        return temp.df
+
+    nfev = []  # track inner function evaluations
+    res = jacobian(df, x, tolerances=tolerances, **kwargs)  # jacobian of jacobian
+
+    nfev = xp.cumulative_sum(xp.stack(nfev), axis=0)
+    res_nit = xp.astype(res.nit[xp.newaxis, ...], xp.int64)  # appease torch
+    res.nfev = xp_take_along_axis(nfev, res_nit, axis=0)[0]
+    res.ddf = res.df
+    del res.df  # this is renamed to ddf
+    del res.nit  # this is only the outer-jacobian nit
+
+    return res

infer_4_30_0/lib/python3.10/site-packages/scipy/differentiate/tests/test_differentiate.py

@@ -0,0 +1,695 @@
+import math
+import pytest
+
+import numpy as np
+
+from scipy.conftest import array_api_compatible
+import scipy._lib._elementwise_iterative_method as eim
+from scipy._lib._array_api_no_0d import xp_assert_close, xp_assert_equal, xp_assert_less
+from scipy._lib._array_api import is_numpy, is_torch, array_namespace
+
+from scipy import stats, optimize, special
+from scipy.differentiate import derivative, jacobian, hessian
+from scipy.differentiate._differentiate import _EERRORINCREASE
+
+
+pytestmark = [array_api_compatible, pytest.mark.usefixtures("skip_xp_backends")]
+
+array_api_strict_skip_reason = 'Array API does not support fancy indexing assignment.'
+jax_skip_reason = 'JAX arrays do not support item assignment.'
+
+
+@pytest.mark.skip_xp_backends('array_api_strict', reason=array_api_strict_skip_reason)
+@pytest.mark.skip_xp_backends('jax.numpy',reason=jax_skip_reason)
+class TestDerivative:
+
+    def f(self, x):
+        return special.ndtr(x)
+
+    @pytest.mark.parametrize('x', [0.6, np.linspace(-0.05, 1.05, 10)])
+    def test_basic(self, x, xp):
+        # Invert distribution CDF and compare against distribution `ppf`
+        default_dtype = xp.asarray(1.).dtype
+        res = derivative(self.f, xp.asarray(x, dtype=default_dtype))
+        ref = xp.asarray(stats.norm().pdf(x), dtype=default_dtype)
+        xp_assert_close(res.df, ref)
+        # This would be nice, but doesn't always work out. `error` is an
+        # estimate, not a bound.
+        if not is_torch(xp):
+            xp_assert_less(xp.abs(res.df - ref), res.error)
+
+    @pytest.mark.skip_xp_backends(np_only=True)
+    @pytest.mark.parametrize('case', stats._distr_params.distcont)
+    def test_accuracy(self, case):
+        distname, params = case
+        dist = getattr(stats, distname)(*params)
+        x = dist.median() + 0.1
+        res = derivative(dist.cdf, x)
+        ref = dist.pdf(x)
+        xp_assert_close(res.df, ref, atol=1e-10)
+
+    @pytest.mark.parametrize('order', [1, 6])
+    @pytest.mark.parametrize('shape', [tuple(), (12,), (3, 4), (3, 2, 2)])
+    def test_vectorization(self, order, shape, xp):
+        # Test for correct functionality, output shapes, and dtypes for various
+        # input shapes.
+        x = np.linspace(-0.05, 1.05, 12).reshape(shape) if shape else 0.6
+        n = np.size(x)
+        state = {}
+
+        @np.vectorize
+        def _derivative_single(x):
+            return derivative(self.f, x, order=order)
+
+        def f(x, *args, **kwargs):
+            state['nit'] += 1
+            state['feval'] += 1 if (x.size == n or x.ndim <=1) else x.shape[-1]
+            return self.f(x, *args, **kwargs)
+
+        state['nit'] = -1
+        state['feval'] = 0
+
+        res = derivative(f, xp.asarray(x, dtype=xp.float64), order=order)
+        refs = _derivative_single(x).ravel()
+
+        ref_x = [ref.x for ref in refs]
+        xp_assert_close(xp.reshape(res.x, (-1,)), xp.asarray(ref_x))
+
+        ref_df = [ref.df for ref in refs]
+        xp_assert_close(xp.reshape(res.df, (-1,)), xp.asarray(ref_df))
+
+        ref_error = [ref.error for ref in refs]
+        xp_assert_close(xp.reshape(res.error, (-1,)), xp.asarray(ref_error),
+                        atol=1e-12)
+
+        ref_success = [bool(ref.success) for ref in refs]
+        xp_assert_equal(xp.reshape(res.success, (-1,)), xp.asarray(ref_success))
+
+        ref_flag = [np.int32(ref.status) for ref in refs]
+        xp_assert_equal(xp.reshape(res.status, (-1,)), xp.asarray(ref_flag))
+
+        ref_nfev = [np.int32(ref.nfev) for ref in refs]
+        xp_assert_equal(xp.reshape(res.nfev, (-1,)), xp.asarray(ref_nfev))
+        if is_numpy(xp):  # can't expect other backends to be exactly the same
+            assert xp.max(res.nfev) == state['feval']
+
+        ref_nit = [np.int32(ref.nit) for ref in refs]
+        xp_assert_equal(xp.reshape(res.nit, (-1,)), xp.asarray(ref_nit))
+        if is_numpy(xp):  # can't expect other backends to be exactly the same
+            assert xp.max(res.nit) == state['nit']
+
+    def test_flags(self, xp):
+        # Test cases that should produce different status flags; show that all
+        # can be produced simultaneously.
+        rng = np.random.default_rng(5651219684984213)
+        def f(xs, js):
+            f.nit += 1
+            funcs = [lambda x: x - 2.5,  # converges
+                     lambda x: xp.exp(x)*rng.random(),  # error increases
+                     lambda x: xp.exp(x),  # reaches maxiter due to order=2
+                     lambda x: xp.full_like(x, xp.nan)]  # stops due to NaN
+            res = [funcs[int(j)](x) for x, j in zip(xs, xp.reshape(js, (-1,)))]
+            return xp.stack(res)
+        f.nit = 0
+
+        args = (xp.arange(4, dtype=xp.int64),)
+        res = derivative(f, xp.ones(4, dtype=xp.float64),
+                         tolerances=dict(rtol=1e-14),
+                         order=2, args=args)
+
+        ref_flags = xp.asarray([eim._ECONVERGED,
+                                _EERRORINCREASE,
+                                eim._ECONVERR,
+                                eim._EVALUEERR], dtype=xp.int32)
+        xp_assert_equal(res.status, ref_flags)
+
+    def test_flags_preserve_shape(self, xp):
+        # Same test as above but using `preserve_shape` option to simplify.
+        rng = np.random.default_rng(5651219684984213)
+        def f(x):
+            out = [x - 2.5,  # converges
+                   xp.exp(x)*rng.random(),  # error increases
+                   xp.exp(x),  # reaches maxiter due to order=2
+                   xp.full_like(x, xp.nan)]  # stops due to NaN
+            return xp.stack(out)
+
+        res = derivative(f, xp.asarray(1, dtype=xp.float64),
+                         tolerances=dict(rtol=1e-14),
+                         order=2, preserve_shape=True)
+
+        ref_flags = xp.asarray([eim._ECONVERGED,
+                                _EERRORINCREASE,
+                                eim._ECONVERR,
+                                eim._EVALUEERR], dtype=xp.int32)
+        xp_assert_equal(res.status, ref_flags)
+
+    def test_preserve_shape(self, xp):
+        # Test `preserve_shape` option
+        def f(x):
+            out = [x, xp.sin(3*x), x+xp.sin(10*x), xp.sin(20*x)*(x-1)**2]
+            return xp.stack(out)
+
+        x = xp.asarray(0.)
+        ref = xp.asarray([xp.asarray(1), 3*xp.cos(3*x), 1+10*xp.cos(10*x),
+                          20*xp.cos(20*x)*(x-1)**2 + 2*xp.sin(20*x)*(x-1)])
+        res = derivative(f, x, preserve_shape=True)
+        xp_assert_close(res.df, ref)
+
+    def test_convergence(self, xp):
+        # Test that the convergence tolerances behave as expected
+        x = xp.asarray(1., dtype=xp.float64)
+        f = special.ndtr
+        ref = float(stats.norm.pdf(1.))
+        tolerances0 = dict(atol=0, rtol=0)
+
+        tolerances = tolerances0.copy()
+        tolerances['atol'] = 1e-3
+        res1 = derivative(f, x, tolerances=tolerances, order=4)
+        assert abs(res1.df - ref) < 1e-3
+        tolerances['atol'] = 1e-6
+        res2 = derivative(f, x, tolerances=tolerances, order=4)
+        assert abs(res2.df - ref) < 1e-6
+        assert abs(res2.df - ref) < abs(res1.df - ref)
+
+        tolerances = tolerances0.copy()
+        tolerances['rtol'] = 1e-3
+        res1 = derivative(f, x, tolerances=tolerances, order=4)
+        assert abs(res1.df - ref) < 1e-3 * ref
+        tolerances['rtol'] = 1e-6
+        res2 = derivative(f, x, tolerances=tolerances, order=4)
+        assert abs(res2.df - ref) < 1e-6 * ref
+        assert abs(res2.df - ref) < abs(res1.df - ref)
+
+    def test_step_parameters(self, xp):
+        # Test that step factors have the expected effect on accuracy
+        x = xp.asarray(1., dtype=xp.float64)
+        f = special.ndtr
+        ref = float(stats.norm.pdf(1.))
+
+        res1 = derivative(f, x, initial_step=0.5, maxiter=1)
+        res2 = derivative(f, x, initial_step=0.05, maxiter=1)
+        assert abs(res2.df - ref) < abs(res1.df - ref)
+
+        res1 = derivative(f, x, step_factor=2, maxiter=1)
+        res2 = derivative(f, x, step_factor=20, maxiter=1)
+        assert abs(res2.df - ref) < abs(res1.df - ref)
+
+        # `step_factor` can be less than 1: `initial_step` is the minimum step
+        kwargs = dict(order=4, maxiter=1, step_direction=0)
+        res = derivative(f, x, initial_step=0.5, step_factor=0.5, **kwargs)
+        ref = derivative(f, x, initial_step=1, step_factor=2, **kwargs)
+        xp_assert_close(res.df, ref.df, rtol=5e-15)
+
+        # This is a similar test for one-sided difference
+        kwargs = dict(order=2, maxiter=1, step_direction=1)
+        res = derivative(f, x, initial_step=1, step_factor=2, **kwargs)
+        ref = derivative(f, x, initial_step=1/np.sqrt(2), step_factor=0.5, **kwargs)
+        xp_assert_close(res.df, ref.df, rtol=5e-15)
+
+        kwargs['step_direction'] = -1
+        res = derivative(f, x, initial_step=1, step_factor=2, **kwargs)
+        ref = derivative(f, x, initial_step=1/np.sqrt(2), step_factor=0.5, **kwargs)
+        xp_assert_close(res.df, ref.df, rtol=5e-15)
+
+    def test_step_direction(self, xp):
+        # test that `step_direction` works as expected
+        def f(x):
+            y = xp.exp(x)
+            y[(x < 0) + (x > 2)] = xp.nan
+            return y
+
+        x = xp.linspace(0, 2, 10)
+        step_direction = xp.zeros_like(x)
+        step_direction[x < 0.6], step_direction[x > 1.4] = 1, -1
+        res = derivative(f, x, step_direction=step_direction)
+        xp_assert_close(res.df, xp.exp(x))
+        assert xp.all(res.success)
+
+    def test_vectorized_step_direction_args(self, xp):
+        # test that `step_direction` and `args` are vectorized properly
+        def f(x, p):
+            return x ** p
+
+        def df(x, p):
+            return p * x ** (p - 1)
+
+        x = xp.reshape(xp.asarray([1, 2, 3, 4]), (-1, 1, 1))
+        hdir = xp.reshape(xp.asarray([-1, 0, 1]), (1, -1, 1))
+        p = xp.reshape(xp.asarray([2, 3]), (1, 1, -1))
+        res = derivative(f, x, step_direction=hdir, args=(p,))
+        ref = xp.broadcast_to(df(x, p), res.df.shape)
+        ref = xp.asarray(ref, dtype=xp.asarray(1.).dtype)
+        xp_assert_close(res.df, ref)
+
+    def test_initial_step(self, xp):
+        # Test that `initial_step` works as expected and is vectorized
+        def f(x):
+            return xp.exp(x)
+
+        x = xp.asarray(0., dtype=xp.float64)
+        step_direction = xp.asarray([-1, 0, 1])
+        h0 = xp.reshape(xp.logspace(-3, 0, 10), (-1, 1))
+        res = derivative(f, x, initial_step=h0, order=2, maxiter=1,
+                         step_direction=step_direction)
+        err = xp.abs(res.df - f(x))
+
+        # error should be smaller for smaller step sizes
+        assert xp.all(err[:-1, ...] < err[1:, ...])
+
+        # results of vectorized call should match results with
+        # initial_step taken one at a time
+        for i in range(h0.shape[0]):
+            ref = derivative(f, x, initial_step=h0[i, 0], order=2, maxiter=1,
+                             step_direction=step_direction)
+            xp_assert_close(res.df[i, :], ref.df, rtol=1e-14)
+
+    def test_maxiter_callback(self, xp):
+        # Test behavior of `maxiter` parameter and `callback` interface
+        x = xp.asarray(0.612814, dtype=xp.float64)
+        maxiter = 3
+
+        def f(x):
+            res = special.ndtr(x)
+            return res
+
+        default_order = 8
+        res = derivative(f, x, maxiter=maxiter, tolerances=dict(rtol=1e-15))
+        assert not xp.any(res.success)
+        assert xp.all(res.nfev == default_order + 1 + (maxiter - 1)*2)
+        assert xp.all(res.nit == maxiter)
+
+        def callback(res):
+            callback.iter += 1
+            callback.res = res
+            assert hasattr(res, 'x')
+            assert float(res.df) not in callback.dfs
+            callback.dfs.add(float(res.df))
+            assert res.status == eim._EINPROGRESS
+            if callback.iter == maxiter:
+                raise StopIteration
+        callback.iter = -1  # callback called once before first iteration
+        callback.res = None
+        callback.dfs = set()
+
+        res2 = derivative(f, x, callback=callback, tolerances=dict(rtol=1e-15))
+        # terminating with callback is identical to terminating due to maxiter
+        # (except for `status`)
+        for key in res.keys():
+            if key == 'status':
+                assert res[key] == eim._ECONVERR
+                assert res2[key] == eim._ECALLBACK
+            else:
+                assert res2[key] == callback.res[key] == res[key]
+
+    @pytest.mark.parametrize("hdir", (-1, 0, 1))
+    @pytest.mark.parametrize("x", (0.65, [0.65, 0.7]))
+    @pytest.mark.parametrize("dtype", ('float16', 'float32', 'float64'))
+    def test_dtype(self, hdir, x, dtype, xp):
+        if dtype == 'float16' and not is_numpy(xp):
+            pytest.skip('float16 not tested for alternative backends')
+
+        # Test that dtypes are preserved
+        dtype = getattr(xp, dtype)
+        x = xp.asarray(x, dtype=dtype)
+
+        def f(x):
+            assert x.dtype == dtype
+            return xp.exp(x)
+
+        def callback(res):
+            assert res.x.dtype == dtype
+            assert res.df.dtype == dtype
+            assert res.error.dtype == dtype
+
+        res = derivative(f, x, order=4, step_direction=hdir, callback=callback)
+        assert res.x.dtype == dtype
+        assert res.df.dtype == dtype
+        assert res.error.dtype == dtype
+        eps = xp.finfo(dtype).eps
+        # not sure why torch is less accurate here; might be worth investigating
+        rtol = eps**0.5 * 50 if is_torch(xp) else eps**0.5
+        xp_assert_close(res.df, xp.exp(res.x), rtol=rtol)
+
+    def test_input_validation(self, xp):
+        # Test input validation for appropriate error messages
+        one = xp.asarray(1)
+
+        message = '`f` must be callable.'
+        with pytest.raises(ValueError, match=message):
+            derivative(None, one)
+
+        message = 'Abscissae and function output must be real numbers.'
+        with pytest.raises(ValueError, match=message):
+            derivative(lambda x: x, xp.asarray(-4+1j))
+
+        message = "When `preserve_shape=False`, the shape of the array..."
+        with pytest.raises(ValueError, match=message):
+            derivative(lambda x: [1, 2, 3], xp.asarray([-2, -3]))
+
+        message = 'Tolerances and step parameters must be non-negative...'
+        with pytest.raises(ValueError, match=message):
+            derivative(lambda x: x, one, tolerances=dict(atol=-1))
+        with pytest.raises(ValueError, match=message):
+            derivative(lambda x: x, one, tolerances=dict(rtol='ekki'))
+        with pytest.raises(ValueError, match=message):
+            derivative(lambda x: x, one, step_factor=object())
+
+        message = '`maxiter` must be a positive integer.'
+        with pytest.raises(ValueError, match=message):
+            derivative(lambda x: x, one, maxiter=1.5)
+        with pytest.raises(ValueError, match=message):
+            derivative(lambda x: x, one, maxiter=0)
+
+        message = '`order` must be a positive integer'
+        with pytest.raises(ValueError, match=message):
+            derivative(lambda x: x, one, order=1.5)
+        with pytest.raises(ValueError, match=message):
+            derivative(lambda x: x, one, order=0)
+
+        message = '`preserve_shape` must be True or False.'
+        with pytest.raises(ValueError, match=message):
+            derivative(lambda x: x, one, preserve_shape='herring')
+
+        message = '`callback` must be callable.'
+        with pytest.raises(ValueError, match=message):
+            derivative(lambda x: x, one, callback='shrubbery')
+
+    def test_special_cases(self, xp):
+        # Test edge cases and other special cases
+
+        # Test that integers are not passed to `f`
+        # (otherwise this would overflow)
+        def f(x):
+            xp_test = array_namespace(x)  # needs `isdtype`
+            assert xp_test.isdtype(x.dtype, 'real floating')
+            return x ** 99 - 1
+
+        if not is_torch(xp):  # torch defaults to float32
+            res = derivative(f, xp.asarray(7), tolerances=dict(rtol=1e-10))
+            assert res.success
+            xp_assert_close(res.df, xp.asarray(99*7.**98))
+
+        # Test invalid step size and direction
+        res = derivative(xp.exp, xp.asarray(1), step_direction=xp.nan)
+        xp_assert_equal(res.df, xp.asarray(xp.nan))
+        xp_assert_equal(res.status, xp.asarray(-3, dtype=xp.int32))
+
+        res = derivative(xp.exp, xp.asarray(1), initial_step=0)
+        xp_assert_equal(res.df, xp.asarray(xp.nan))
+        xp_assert_equal(res.status, xp.asarray(-3, dtype=xp.int32))
+
+        # Test that if success is achieved in the correct number
+        # of iterations if function is a polynomial. Ideally, all polynomials
+        # of order 0-2 would get exact result with 0 refinement iterations,
+        # all polynomials of order 3-4 would be differentiated exactly after
+        # 1 iteration, etc. However, it seems that `derivative` needs an
+        # extra iteration to detect convergence based on the error estimate.
+
+        for n in range(6):
+            x = xp.asarray(1.5, dtype=xp.float64)
+            def f(x):
+                return 2*x**n
+
+            ref = 2*n*x**(n-1)
+
+            res = derivative(f, x, maxiter=1, order=max(1, n))
+            xp_assert_close(res.df, ref, rtol=1e-15)
+            xp_assert_equal(res.error, xp.asarray(xp.nan, dtype=xp.float64))
+
+            res = derivative(f, x, order=max(1, n))
+            assert res.success
+            assert res.nit == 2
+            xp_assert_close(res.df, ref, rtol=1e-15)
+
+        # Test scalar `args` (not in tuple)
+        def f(x, c):
+            return c*x - 1
+
+        res = derivative(f, xp.asarray(2), args=xp.asarray(3))
+        xp_assert_close(res.df, xp.asarray(3.))
+
+    # no need to run a test on multiple backends if it's xfailed
+    @pytest.mark.skip_xp_backends(np_only=True)
+    @pytest.mark.xfail
+    @pytest.mark.parametrize("case", (  # function, evaluation point
+        (lambda x: (x - 1) ** 3, 1),
+        (lambda x: np.where(x > 1, (x - 1) ** 5, (x - 1) ** 3), 1)
+    ))
+    def test_saddle_gh18811(self, case):
+        # With default settings, `derivative` will not always converge when
+        # the true derivative is exactly zero. This tests that specifying a
+        # (tight) `atol` alleviates the problem. See discussion in gh-18811.
+        atol = 1e-16
+        res = derivative(*case, step_direction=[-1, 0, 1], atol=atol)
+        assert np.all(res.success)
+        xp_assert_close(res.df, 0, atol=atol)
+
+
+class JacobianHessianTest:
+    def test_iv(self, xp):
+        jh_func = self.jh_func.__func__
+
+        # Test input validation
+        message = "Argument `x` must be at least 1-D."
+        with pytest.raises(ValueError, match=message):
+            jh_func(xp.sin, 1, tolerances=dict(atol=-1))
+
+        # Confirm that other parameters are being passed to `derivative`,
+        # which raises an appropriate error message.
+        x = xp.ones(3)
+        func = optimize.rosen
+        message = 'Tolerances and step parameters must be non-negative scalars.'
+        with pytest.raises(ValueError, match=message):
+            jh_func(func, x, tolerances=dict(atol=-1))
+        with pytest.raises(ValueError, match=message):
+            jh_func(func, x, tolerances=dict(rtol=-1))
+        with pytest.raises(ValueError, match=message):
+            jh_func(func, x, step_factor=-1)
+
+        message = '`order` must be a positive integer.'
+        with pytest.raises(ValueError, match=message):
+            jh_func(func, x, order=-1)
+
+        message = '`maxiter` must be a positive integer.'
+        with pytest.raises(ValueError, match=message):
+            jh_func(func, x, maxiter=-1)
+
+
+@pytest.mark.skip_xp_backends('array_api_strict', reason=array_api_strict_skip_reason)
+@pytest.mark.skip_xp_backends('jax.numpy',reason=jax_skip_reason)
+class TestJacobian(JacobianHessianTest):
+    jh_func = jacobian
+
+    # Example functions and Jacobians from Wikipedia:
+    # https://en.wikipedia.org/wiki/Jacobian_matrix_and_determinant#Examples
+
+    def f1(z, xp):
+        x, y = z
+        return xp.stack([x ** 2 * y, 5 * x + xp.sin(y)])
+
+    def df1(z):
+        x, y = z
+        return [[2 * x * y, x ** 2], [np.full_like(x, 5), np.cos(y)]]
+
+    f1.mn = 2, 2  # type: ignore[attr-defined]
+    f1.ref = df1  # type: ignore[attr-defined]
+
+    def f2(z, xp):
+        r, phi = z
+        return xp.stack([r * xp.cos(phi), r * xp.sin(phi)])
+
+    def df2(z):
+        r, phi = z
+        return [[np.cos(phi), -r * np.sin(phi)],
+                [np.sin(phi), r * np.cos(phi)]]
+
+    f2.mn = 2, 2  # type: ignore[attr-defined]
+    f2.ref = df2  # type: ignore[attr-defined]
+
+    def f3(z, xp):
+        r, phi, th = z
+        return xp.stack([r * xp.sin(phi) * xp.cos(th), r * xp.sin(phi) * xp.sin(th),
+                         r * xp.cos(phi)])
+
+    def df3(z):
+        r, phi, th = z
+        return [[np.sin(phi) * np.cos(th), r * np.cos(phi) * np.cos(th),
+                 -r * np.sin(phi) * np.sin(th)],
+                [np.sin(phi) * np.sin(th), r * np.cos(phi) * np.sin(th),
+                 r * np.sin(phi) * np.cos(th)],
+                [np.cos(phi), -r * np.sin(phi), np.zeros_like(r)]]
+
+    f3.mn = 3, 3  # type: ignore[attr-defined]
+    f3.ref = df3  # type: ignore[attr-defined]
+
+    def f4(x, xp):
+        x1, x2, x3 = x
+        return xp.stack([x1, 5 * x3, 4 * x2 ** 2 - 2 * x3, x3 * xp.sin(x1)])
+
+    def df4(x):
+        x1, x2, x3 = x
+        one = np.ones_like(x1)
+        return [[one, 0 * one, 0 * one],
+                [0 * one, 0 * one, 5 * one],
+                [0 * one, 8 * x2, -2 * one],
+                [x3 * np.cos(x1), 0 * one, np.sin(x1)]]
+
+    f4.mn = 3, 4  # type: ignore[attr-defined]
+    f4.ref = df4  # type: ignore[attr-defined]
+
+    def f5(x, xp):
+        x1, x2, x3 = x
+        return xp.stack([5 * x2, 4 * x1 ** 2 - 2 * xp.sin(x2 * x3), x2 * x3])
+
+    def df5(x):
+        x1, x2, x3 = x
+        one = np.ones_like(x1)
+        return [[0 * one, 5 * one, 0 * one],
+                [8 * x1, -2 * x3 * np.cos(x2 * x3), -2 * x2 * np.cos(x2 * x3)],
+                [0 * one, x3, x2]]
+
+    f5.mn = 3, 3  # type: ignore[attr-defined]
+    f5.ref = df5  # type: ignore[attr-defined]
+
+    def rosen(x, _): return optimize.rosen(x)
+    rosen.mn = 5, 1  # type: ignore[attr-defined]
+    rosen.ref = optimize.rosen_der  # type: ignore[attr-defined]
+
+    @pytest.mark.parametrize('dtype', ('float32', 'float64'))
+    @pytest.mark.parametrize('size', [(), (6,), (2, 3)])
+    @pytest.mark.parametrize('func', [f1, f2, f3, f4, f5, rosen])
+    def test_examples(self, dtype, size, func, xp):
+        atol = 1e-10 if dtype == 'float64' else 1.99e-3
+        dtype = getattr(xp, dtype)
+        rng = np.random.default_rng(458912319542)
+        m, n = func.mn
+        x = rng.random(size=(m,) + size)
+        res = jacobian(lambda x: func(x , xp), xp.asarray(x, dtype=dtype))
+        # convert list of arrays to single array before converting to xp array
+        ref = xp.asarray(np.asarray(func.ref(x)), dtype=dtype)
+        xp_assert_close(res.df, ref, atol=atol)
+
+    def test_attrs(self, xp):
+        # Test attributes of result object
+        z = xp.asarray([0.5, 0.25])
+
+        # case in which some elements of the Jacobian are harder
+        # to calculate than others
+        def df1(z):
+            x, y = z
+            return xp.stack([xp.cos(0.5*x) * xp.cos(y), xp.sin(2*x) * y**2])
+
+        def df1_0xy(x, y):
+            return xp.cos(0.5*x) * xp.cos(y)
+
+        def df1_1xy(x, y):
+            return xp.sin(2*x) * y**2
+
+        res = jacobian(df1, z, initial_step=10)
+        if is_numpy(xp):
+            assert len(np.unique(res.nit)) == 4
+            assert len(np.unique(res.nfev)) == 4
+
+        res00 = jacobian(lambda x: df1_0xy(x, z[1]), z[0:1], initial_step=10)
+        res01 = jacobian(lambda y: df1_0xy(z[0], y), z[1:2], initial_step=10)
+        res10 = jacobian(lambda x: df1_1xy(x, z[1]), z[0:1], initial_step=10)
+        res11 = jacobian(lambda y: df1_1xy(z[0], y), z[1:2], initial_step=10)
+        ref = optimize.OptimizeResult()
+        for attr in ['success', 'status', 'df', 'nit', 'nfev']:
+            ref_attr = xp.asarray([[getattr(res00, attr), getattr(res01, attr)],
+                                   [getattr(res10, attr), getattr(res11, attr)]])
+            ref[attr] = xp.squeeze(ref_attr)
+            rtol = 1.5e-5 if res[attr].dtype == xp.float32 else 1.5e-14
+            xp_assert_close(res[attr], ref[attr], rtol=rtol)
+
+    def test_step_direction_size(self, xp):
+        # Check that `step_direction` and `initial_step` can be used to ensure that
+        # the usable domain of a function is respected.
+        rng = np.random.default_rng(23892589425245)
+        b = rng.random(3)
+        eps = 1e-7  # torch needs wiggle room?
+
+        def f(x):
+            x[0, x[0] < b[0]] = xp.nan
+            x[0, x[0] > b[0] + 0.25] = xp.nan
+            x[1, x[1] > b[1]] = xp.nan
+            x[1, x[1] < b[1] - 0.1-eps] = xp.nan
+            return TestJacobian.f5(x, xp)
+
+        dir = [1, -1, 0]
+        h0 = [0.25, 0.1, 0.5]
+        atol = {'atol': 1e-8}
+        res = jacobian(f, xp.asarray(b, dtype=xp.float64), initial_step=h0,
+                       step_direction=dir, tolerances=atol)
+        ref = xp.asarray(TestJacobian.df5(b), dtype=xp.float64)
+        xp_assert_close(res.df, ref, atol=1e-8)
+        assert xp.all(xp.isfinite(ref))
+
+
+@pytest.mark.skip_xp_backends('array_api_strict', reason=array_api_strict_skip_reason)
+@pytest.mark.skip_xp_backends('jax.numpy',reason=jax_skip_reason)
+class TestHessian(JacobianHessianTest):
+    jh_func = hessian
+
+    @pytest.mark.parametrize('shape', [(), (4,), (2, 4)])
+    def test_example(self, shape, xp):
+        rng = np.random.default_rng(458912319542)
+        m = 3
+        x = xp.asarray(rng.random((m,) + shape), dtype=xp.float64)
+        res = hessian(optimize.rosen, x)
+        if shape:
+            x = xp.reshape(x, (m, -1))
+            ref = xp.stack([optimize.rosen_hess(xi) for xi in x.T])
+            ref = xp.moveaxis(ref, 0, -1)
+            ref = xp.reshape(ref, (m, m,) + shape)
+        else:
+            ref = optimize.rosen_hess(x)
+        xp_assert_close(res.ddf, ref, atol=1e-8)
+
+        # # Removed symmetry enforcement; consider adding back in as a feature
+        # # check symmetry
+        # for key in ['ddf', 'error', 'nfev', 'success', 'status']:
+        #     assert_equal(res[key], np.swapaxes(res[key], 0, 1))
+
+    def test_float32(self, xp):
+        rng = np.random.default_rng(458912319542)
+        x = xp.asarray(rng.random(3), dtype=xp.float32)
+        res = hessian(optimize.rosen, x)
+        ref = optimize.rosen_hess(x)
+        mask = (ref != 0)
+        xp_assert_close(res.ddf[mask], ref[mask])
+        atol = 1e-2 * xp.abs(xp.min(ref[mask]))
+        xp_assert_close(res.ddf[~mask], ref[~mask], atol=atol)
+
+    def test_nfev(self, xp):
+        z = xp.asarray([0.5, 0.25])
+        xp_test = array_namespace(z)
+
+        def f1(z):
+            x, y = xp_test.broadcast_arrays(*z)
+            f1.nfev = f1.nfev + (math.prod(x.shape[2:]) if x.ndim > 2 else 1)
+            return xp.sin(x) * y ** 3
+        f1.nfev = 0
+
+
+        res = hessian(f1, z, initial_step=10)
+        f1.nfev = 0
+        res00 = hessian(lambda x: f1([x[0], z[1]]), z[0:1], initial_step=10)
+        assert res.nfev[0, 0] == f1.nfev == res00.nfev[0, 0]
+
+        f1.nfev = 0
+        res11 = hessian(lambda y: f1([z[0], y[0]]), z[1:2], initial_step=10)
+        assert res.nfev[1, 1] == f1.nfev == res11.nfev[0, 0]
+
+        # Removed symmetry enforcement; consider adding back in as a feature
+        # assert_equal(res.nfev, res.nfev.T)  # check symmetry
+        # assert np.unique(res.nfev).size == 3
+
+
+    @pytest.mark.thread_unsafe
+    @pytest.mark.skip_xp_backends(np_only=True,
+                                  reason='Python list input uses NumPy backend')
+    def test_small_rtol_warning(self, xp):
+        message = 'The specified `rtol=1e-15`, but...'
+        with pytest.warns(RuntimeWarning, match=message):
+            hessian(xp.sin, [1.], tolerances=dict(rtol=1e-15))

infer_4_30_0/lib/python3.10/site-packages/scipy/io/arff/tests/data/nodata.arff

@@ -0,0 +1,11 @@
+@RELATION iris
+
+@ATTRIBUTE sepallength  REAL
+@ATTRIBUTE sepalwidth   REAL
+@ATTRIBUTE petallength  REAL
+@ATTRIBUTE petalwidth   REAL
+@ATTRIBUTE class    {Iris-setosa,Iris-versicolor,Iris-virginica}
+
+@DATA
+
+% This file has no data

infer_4_30_0/lib/python3.10/site-packages/scipy/io/arff/tests/data/test2.arff

@@ -0,0 +1,15 @@
+@RELATION test2
+
+@ATTRIBUTE attr0	REAL
+@ATTRIBUTE attr1 	real
+@ATTRIBUTE attr2 	integer
+@ATTRIBUTE attr3	Integer
+@ATTRIBUTE attr4 	Numeric
+@ATTRIBUTE attr5	numeric
+@ATTRIBUTE attr6 	string
+@ATTRIBUTE attr7 	STRING
+@ATTRIBUTE attr8 	{bla}
+@ATTRIBUTE attr9 	{bla, bla}
+
+@DATA
+0.1, 0.2, 0.3, 0.4,class1

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/__init__.py

@@ -0,0 +1,327 @@
+"""
+=======================================
+Signal processing (:mod:`scipy.signal`)
+=======================================
+
+Convolution
+===========
+
+.. autosummary::
+   :toctree: generated/
+
+   convolve           -- N-D convolution.
+   correlate          -- N-D correlation.
+   fftconvolve        -- N-D convolution using the FFT.
+   oaconvolve         -- N-D convolution using the overlap-add method.
+   convolve2d         -- 2-D convolution (more options).
+   correlate2d        -- 2-D correlation (more options).
+   sepfir2d           -- Convolve with a 2-D separable FIR filter.
+   choose_conv_method -- Chooses faster of FFT and direct convolution methods.
+   correlation_lags   -- Determines lag indices for 1D cross-correlation.
+
+B-splines
+=========
+
+.. autosummary::
+   :toctree: generated/
+
+   gauss_spline   -- Gaussian approximation to the B-spline basis function.
+   cspline1d      -- Coefficients for 1-D cubic (3rd order) B-spline.
+   qspline1d      -- Coefficients for 1-D quadratic (2nd order) B-spline.
+   cspline2d      -- Coefficients for 2-D cubic (3rd order) B-spline.
+   qspline2d      -- Coefficients for 2-D quadratic (2nd order) B-spline.
+   cspline1d_eval -- Evaluate a cubic spline at the given points.
+   qspline1d_eval -- Evaluate a quadratic spline at the given points.
+   spline_filter  -- Smoothing spline (cubic) filtering of a rank-2 array.
+
+Filtering
+=========
+
+.. autosummary::
+   :toctree: generated/
+
+   order_filter  -- N-D order filter.
+   medfilt       -- N-D median filter.
+   medfilt2d     -- 2-D median filter (faster).
+   wiener        -- N-D Wiener filter.
+
+   symiirorder1  -- 2nd-order IIR filter (cascade of first-order systems).
+   symiirorder2  -- 4th-order IIR filter (cascade of second-order systems).
+   lfilter       -- 1-D FIR and IIR digital linear filtering.
+   lfiltic       -- Construct initial conditions for `lfilter`.
+   lfilter_zi    -- Compute an initial state zi for the lfilter function that
+                 -- corresponds to the steady state of the step response.
+   filtfilt      -- A forward-backward filter.
+   savgol_filter -- Filter a signal using the Savitzky-Golay filter.
+
+   deconvolve    -- 1-D deconvolution using lfilter.
+
+   sosfilt       -- 1-D IIR digital linear filtering using
+                 -- a second-order sections filter representation.
+   sosfilt_zi    -- Compute an initial state zi for the sosfilt function that
+                 -- corresponds to the steady state of the step response.
+   sosfiltfilt   -- A forward-backward filter for second-order sections.
+   hilbert       -- Compute 1-D analytic signal, using the Hilbert transform.
+   hilbert2      -- Compute 2-D analytic signal, using the Hilbert transform.
+   envelope      -- Compute the envelope of a real- or complex-valued signal.
+
+   decimate      -- Downsample a signal.
+   detrend       -- Remove linear and/or constant trends from data.
+   resample      -- Resample using Fourier method.
+   resample_poly -- Resample using polyphase filtering method.
+   upfirdn       -- Upsample, apply FIR filter, downsample.
+
+Filter design
+=============
+
+.. autosummary::
+   :toctree: generated/
+
+   bilinear      -- Digital filter from an analog filter using
+                    -- the bilinear transform.
+   bilinear_zpk  -- Digital filter from an analog filter using
+                    -- the bilinear transform.
+   findfreqs     -- Find array of frequencies for computing filter response.
+   firls         -- FIR filter design using least-squares error minimization.
+   firwin        -- Windowed FIR filter design, with frequency response
+                    -- defined as pass and stop bands.
+   firwin2       -- Windowed FIR filter design, with arbitrary frequency
+                    -- response.
+   freqs         -- Analog filter frequency response from TF coefficients.
+   freqs_zpk     -- Analog filter frequency response from ZPK coefficients.
+   freqz         -- Digital filter frequency response from TF coefficients.
+   freqz_sos     -- Digital filter frequency response for SOS format filter.
+   freqz_zpk     -- Digital filter frequency response from ZPK coefficients.
+   gammatone     -- FIR and IIR gammatone filter design.
+   group_delay   -- Digital filter group delay.
+   iirdesign     -- IIR filter design given bands and gains.
+   iirfilter     -- IIR filter design given order and critical frequencies.
+   kaiser_atten  -- Compute the attenuation of a Kaiser FIR filter, given
+                    -- the number of taps and the transition width at
+                    -- discontinuities in the frequency response.
+   kaiser_beta   -- Compute the Kaiser parameter beta, given the desired
+                    -- FIR filter attenuation.
+   kaiserord     -- Design a Kaiser window to limit ripple and width of
+                    -- transition region.
+   minimum_phase -- Convert a linear phase FIR filter to minimum phase.
+   savgol_coeffs -- Compute the FIR filter coefficients for a Savitzky-Golay
+                    -- filter.
+   remez         -- Optimal FIR filter design.
+
+   unique_roots  -- Unique roots and their multiplicities.
+   residue       -- Partial fraction expansion of b(s) / a(s).
+   residuez      -- Partial fraction expansion of b(z) / a(z).
+   invres        -- Inverse partial fraction expansion for analog filter.
+   invresz       -- Inverse partial fraction expansion for digital filter.
+   BadCoefficients  -- Warning on badly conditioned filter coefficients.
+
+Lower-level filter design functions:
+
+.. autosummary::
+   :toctree: generated/
+
+   abcd_normalize -- Check state-space matrices and ensure they are rank-2.
+   band_stop_obj  -- Band Stop Objective Function for order minimization.
+   besselap       -- Return (z,p,k) for analog prototype of Bessel filter.
+   buttap         -- Return (z,p,k) for analog prototype of Butterworth filter.
+   cheb1ap        -- Return (z,p,k) for type I Chebyshev filter.
+   cheb2ap        -- Return (z,p,k) for type II Chebyshev filter.
+   ellipap        -- Return (z,p,k) for analog prototype of elliptic filter.
+   lp2bp          -- Transform a lowpass filter prototype to a bandpass filter.
+   lp2bp_zpk      -- Transform a lowpass filter prototype to a bandpass filter.
+   lp2bs          -- Transform a lowpass filter prototype to a bandstop filter.
+   lp2bs_zpk      -- Transform a lowpass filter prototype to a bandstop filter.
+   lp2hp          -- Transform a lowpass filter prototype to a highpass filter.
+   lp2hp_zpk      -- Transform a lowpass filter prototype to a highpass filter.
+   lp2lp          -- Transform a lowpass filter prototype to a lowpass filter.
+   lp2lp_zpk      -- Transform a lowpass filter prototype to a lowpass filter.
+   normalize      -- Normalize polynomial representation of a transfer function.
+
+
+
+Matlab-style IIR filter design
+==============================
+
+.. autosummary::
+   :toctree: generated/
+
+   butter -- Butterworth
+   buttord
+   cheby1 -- Chebyshev Type I
+   cheb1ord
+   cheby2 -- Chebyshev Type II
+   cheb2ord
+   ellip -- Elliptic (Cauer)
+   ellipord
+   bessel -- Bessel (no order selection available -- try butterod)
+   iirnotch      -- Design second-order IIR notch digital filter.
+   iirpeak       -- Design second-order IIR peak (resonant) digital filter.
+   iircomb       -- Design IIR comb filter.
+
+Continuous-time linear systems
+==============================
+
+.. autosummary::
+   :toctree: generated/
+
+   lti              -- Continuous-time linear time invariant system base class.
+   StateSpace       -- Linear time invariant system in state space form.
+   TransferFunction -- Linear time invariant system in transfer function form.
+   ZerosPolesGain   -- Linear time invariant system in zeros, poles, gain form.
+   lsim             -- Continuous-time simulation of output to linear system.
+   impulse          -- Impulse response of linear, time-invariant (LTI) system.
+   step             -- Step response of continuous-time LTI system.
+   freqresp         -- Frequency response of a continuous-time LTI system.
+   bode             -- Bode magnitude and phase data (continuous-time LTI).
+
+Discrete-time linear systems
+============================
+
+.. autosummary::
+   :toctree: generated/
+
+   dlti             -- Discrete-time linear time invariant system base class.
+   StateSpace       -- Linear time invariant system in state space form.
+   TransferFunction -- Linear time invariant system in transfer function form.
+   ZerosPolesGain   -- Linear time invariant system in zeros, poles, gain form.
+   dlsim            -- Simulation of output to a discrete-time linear system.
+   dimpulse         -- Impulse response of a discrete-time LTI system.
+   dstep            -- Step response of a discrete-time LTI system.
+   dfreqresp        -- Frequency response of a discrete-time LTI system.
+   dbode            -- Bode magnitude and phase data (discrete-time LTI).
+
+LTI representations
+===================
+
+.. autosummary::
+   :toctree: generated/
+
+   tf2zpk        -- Transfer function to zero-pole-gain.
+   tf2sos        -- Transfer function to second-order sections.
+   tf2ss         -- Transfer function to state-space.
+   zpk2tf        -- Zero-pole-gain to transfer function.
+   zpk2sos       -- Zero-pole-gain to second-order sections.
+   zpk2ss        -- Zero-pole-gain to state-space.
+   ss2tf         -- State-pace to transfer function.
+   ss2zpk        -- State-space to pole-zero-gain.
+   sos2zpk       -- Second-order sections to zero-pole-gain.
+   sos2tf        -- Second-order sections to transfer function.
+   cont2discrete -- Continuous-time to discrete-time LTI conversion.
+   place_poles   -- Pole placement.
+
+Waveforms
+=========
+
+.. autosummary::
+   :toctree: generated/
+
+   chirp        -- Frequency swept cosine signal, with several freq functions.
+   gausspulse   -- Gaussian modulated sinusoid.
+   max_len_seq  -- Maximum length sequence.
+   sawtooth     -- Periodic sawtooth.
+   square       -- Square wave.
+   sweep_poly   -- Frequency swept cosine signal; freq is arbitrary polynomial.
+   unit_impulse -- Discrete unit impulse.
+
+Window functions
+================
+
+For window functions, see the `scipy.signal.windows` namespace.
+
+In the `scipy.signal` namespace, there is a convenience function to
+obtain these windows by name:
+
+.. autosummary::
+   :toctree: generated/
+
+   get_window -- Return a window of a given length and type.
+
+Peak finding
+============
+
+.. autosummary::
+   :toctree: generated/
+
+   argrelmin        -- Calculate the relative minima of data.
+   argrelmax        -- Calculate the relative maxima of data.
+   argrelextrema    -- Calculate the relative extrema of data.
+   find_peaks       -- Find a subset of peaks inside a signal.
+   find_peaks_cwt   -- Find peaks in a 1-D array with wavelet transformation.
+   peak_prominences -- Calculate the prominence of each peak in a signal.
+   peak_widths      -- Calculate the width of each peak in a signal.
+
+Spectral analysis
+=================
+
+.. autosummary::
+   :toctree: generated/
+
+   periodogram    -- Compute a (modified) periodogram.
+   welch          -- Compute a periodogram using Welch's method.
+   csd            -- Compute the cross spectral density, using Welch's method.
+   coherence      -- Compute the magnitude squared coherence, using Welch's method.
+   spectrogram    -- Compute the spectrogram (legacy).
+   lombscargle    -- Computes the Lomb-Scargle periodogram.
+   vectorstrength -- Computes the vector strength.
+   ShortTimeFFT   -- Interface for calculating the \
+                     :ref:`Short Time Fourier Transform <tutorial_stft>` and \
+                     its inverse.
+   stft           -- Compute the Short Time Fourier Transform (legacy).
+   istft          -- Compute the Inverse Short Time Fourier Transform (legacy).
+   check_COLA     -- Check the COLA constraint for iSTFT reconstruction.
+   check_NOLA     -- Check the NOLA constraint for iSTFT reconstruction.
+
+Chirp Z-transform and Zoom FFT
+============================================
+
+.. autosummary::
+   :toctree: generated/
+
+   czt - Chirp z-transform convenience function
+   zoom_fft - Zoom FFT convenience function
+   CZT - Chirp z-transform function generator
+   ZoomFFT - Zoom FFT function generator
+   czt_points - Output the z-plane points sampled by a chirp z-transform
+
+The functions are simpler to use than the classes, but are less efficient when
+using the same transform on many arrays of the same length, since they
+repeatedly generate the same chirp signal with every call.  In these cases,
+use the classes to create a reusable function instead.
+
+"""
+
+from . import _sigtools, windows
+from ._waveforms import *
+from ._max_len_seq import max_len_seq
+from ._upfirdn import upfirdn
+
+from ._spline import (
+    sepfir2d
+)
+
+from ._spline_filters import *
+from ._filter_design import *
+from ._fir_filter_design import *
+from ._ltisys import *
+from ._lti_conversion import *
+from ._signaltools import *
+from ._savitzky_golay import savgol_coeffs, savgol_filter
+from ._spectral_py import *
+from ._short_time_fft import *
+from ._peak_finding import *
+from ._czt import *
+from .windows import get_window  # keep this one in signal namespace
+
+# Deprecated namespaces, to be removed in v2.0.0
+from . import (
+    bsplines, filter_design, fir_filter_design, lti_conversion, ltisys,
+    spectral, signaltools, waveforms, wavelets, spline
+)
+
+__all__ = [
+    s for s in dir() if not s.startswith("_")
+]
+
+from scipy._lib._testutils import PytestTester
+test = PytestTester(__name__)
+del PytestTester

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_arraytools.py

@@ -0,0 +1,264 @@
+"""
+Functions for acting on a axis of an array.
+"""
+import numpy as np
+
+
+def axis_slice(a, start=None, stop=None, step=None, axis=-1):
+    """Take a slice along axis 'axis' from 'a'.
+
+    Parameters
+    ----------
+    a : numpy.ndarray
+        The array to be sliced.
+    start, stop, step : int or None
+        The slice parameters.
+    axis : int, optional
+        The axis of `a` to be sliced.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal._arraytools import axis_slice
+    >>> a = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
+    >>> axis_slice(a, start=0, stop=1, axis=1)
+    array([[1],
+           [4],
+           [7]])
+    >>> axis_slice(a, start=1, axis=0)
+    array([[4, 5, 6],
+           [7, 8, 9]])
+
+    Notes
+    -----
+    The keyword arguments start, stop and step are used by calling
+    slice(start, stop, step). This implies axis_slice() does not
+    handle its arguments the exactly the same as indexing. To select
+    a single index k, for example, use
+        axis_slice(a, start=k, stop=k+1)
+    In this case, the length of the axis 'axis' in the result will
+    be 1; the trivial dimension is not removed. (Use numpy.squeeze()
+    to remove trivial axes.)
+    """
+    a_slice = [slice(None)] * a.ndim
+    a_slice[axis] = slice(start, stop, step)
+    b = a[tuple(a_slice)]
+    return b
+
+
+def axis_reverse(a, axis=-1):
+    """Reverse the 1-D slices of `a` along axis `axis`.
+
+    Returns axis_slice(a, step=-1, axis=axis).
+    """
+    return axis_slice(a, step=-1, axis=axis)
+
+
+def odd_ext(x, n, axis=-1):
+    """
+    Odd extension at the boundaries of an array
+
+    Generate a new ndarray by making an odd extension of `x` along an axis.
+
+    Parameters
+    ----------
+    x : ndarray
+        The array to be extended.
+    n : int
+        The number of elements by which to extend `x` at each end of the axis.
+    axis : int, optional
+        The axis along which to extend `x`. Default is -1.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal._arraytools import odd_ext
+    >>> a = np.array([[1, 2, 3, 4, 5], [0, 1, 4, 9, 16]])
+    >>> odd_ext(a, 2)
+    array([[-1,  0,  1,  2,  3,  4,  5,  6,  7],
+           [-4, -1,  0,  1,  4,  9, 16, 23, 28]])
+
+    Odd extension is a "180 degree rotation" at the endpoints of the original
+    array:
+
+    >>> t = np.linspace(0, 1.5, 100)
+    >>> a = 0.9 * np.sin(2 * np.pi * t**2)
+    >>> b = odd_ext(a, 40)
+    >>> import matplotlib.pyplot as plt
+    >>> plt.plot(np.arange(-40, 140), b, 'b', lw=1, label='odd extension')
+    >>> plt.plot(np.arange(100), a, 'r', lw=2, label='original')
+    >>> plt.legend(loc='best')
+    >>> plt.show()
+    """
+    if n < 1:
+        return x
+    if n > x.shape[axis] - 1:
+        raise ValueError(("The extension length n (%d) is too big. " +
+                         "It must not exceed x.shape[axis]-1, which is %d.")
+                         % (n, x.shape[axis] - 1))
+    left_end = axis_slice(x, start=0, stop=1, axis=axis)
+    left_ext = axis_slice(x, start=n, stop=0, step=-1, axis=axis)
+    right_end = axis_slice(x, start=-1, axis=axis)
+    right_ext = axis_slice(x, start=-2, stop=-(n + 2), step=-1, axis=axis)
+    ext = np.concatenate((2 * left_end - left_ext,
+                          x,
+                          2 * right_end - right_ext),
+                         axis=axis)
+    return ext
+
+
+def even_ext(x, n, axis=-1):
+    """
+    Even extension at the boundaries of an array
+
+    Generate a new ndarray by making an even extension of `x` along an axis.
+
+    Parameters
+    ----------
+    x : ndarray
+        The array to be extended.
+    n : int
+        The number of elements by which to extend `x` at each end of the axis.
+    axis : int, optional
+        The axis along which to extend `x`. Default is -1.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal._arraytools import even_ext
+    >>> a = np.array([[1, 2, 3, 4, 5], [0, 1, 4, 9, 16]])
+    >>> even_ext(a, 2)
+    array([[ 3,  2,  1,  2,  3,  4,  5,  4,  3],
+           [ 4,  1,  0,  1,  4,  9, 16,  9,  4]])
+
+    Even extension is a "mirror image" at the boundaries of the original array:
+
+    >>> t = np.linspace(0, 1.5, 100)
+    >>> a = 0.9 * np.sin(2 * np.pi * t**2)
+    >>> b = even_ext(a, 40)
+    >>> import matplotlib.pyplot as plt
+    >>> plt.plot(np.arange(-40, 140), b, 'b', lw=1, label='even extension')
+    >>> plt.plot(np.arange(100), a, 'r', lw=2, label='original')
+    >>> plt.legend(loc='best')
+    >>> plt.show()
+    """
+    if n < 1:
+        return x
+    if n > x.shape[axis] - 1:
+        raise ValueError(("The extension length n (%d) is too big. " +
+                         "It must not exceed x.shape[axis]-1, which is %d.")
+                         % (n, x.shape[axis] - 1))
+    left_ext = axis_slice(x, start=n, stop=0, step=-1, axis=axis)
+    right_ext = axis_slice(x, start=-2, stop=-(n + 2), step=-1, axis=axis)
+    ext = np.concatenate((left_ext,
+                          x,
+                          right_ext),
+                         axis=axis)
+    return ext
+
+
+def const_ext(x, n, axis=-1):
+    """
+    Constant extension at the boundaries of an array
+
+    Generate a new ndarray that is a constant extension of `x` along an axis.
+
+    The extension repeats the values at the first and last element of
+    the axis.
+
+    Parameters
+    ----------
+    x : ndarray
+        The array to be extended.
+    n : int
+        The number of elements by which to extend `x` at each end of the axis.
+    axis : int, optional
+        The axis along which to extend `x`. Default is -1.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal._arraytools import const_ext
+    >>> a = np.array([[1, 2, 3, 4, 5], [0, 1, 4, 9, 16]])
+    >>> const_ext(a, 2)
+    array([[ 1,  1,  1,  2,  3,  4,  5,  5,  5],
+           [ 0,  0,  0,  1,  4,  9, 16, 16, 16]])
+
+    Constant extension continues with the same values as the endpoints of the
+    array:
+
+    >>> t = np.linspace(0, 1.5, 100)
+    >>> a = 0.9 * np.sin(2 * np.pi * t**2)
+    >>> b = const_ext(a, 40)
+    >>> import matplotlib.pyplot as plt
+    >>> plt.plot(np.arange(-40, 140), b, 'b', lw=1, label='constant extension')
+    >>> plt.plot(np.arange(100), a, 'r', lw=2, label='original')
+    >>> plt.legend(loc='best')
+    >>> plt.show()
+    """
+    if n < 1:
+        return x
+    left_end = axis_slice(x, start=0, stop=1, axis=axis)
+    ones_shape = [1] * x.ndim
+    ones_shape[axis] = n
+    ones = np.ones(ones_shape, dtype=x.dtype)
+    left_ext = ones * left_end
+    right_end = axis_slice(x, start=-1, axis=axis)
+    right_ext = ones * right_end
+    ext = np.concatenate((left_ext,
+                          x,
+                          right_ext),
+                         axis=axis)
+    return ext
+
+
+def zero_ext(x, n, axis=-1):
+    """
+    Zero padding at the boundaries of an array
+
+    Generate a new ndarray that is a zero-padded extension of `x` along
+    an axis.
+
+    Parameters
+    ----------
+    x : ndarray
+        The array to be extended.
+    n : int
+        The number of elements by which to extend `x` at each end of the
+        axis.
+    axis : int, optional
+        The axis along which to extend `x`. Default is -1.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal._arraytools import zero_ext
+    >>> a = np.array([[1, 2, 3, 4, 5], [0, 1, 4, 9, 16]])
+    >>> zero_ext(a, 2)
+    array([[ 0,  0,  1,  2,  3,  4,  5,  0,  0],
+           [ 0,  0,  0,  1,  4,  9, 16,  0,  0]])
+    """
+    if n < 1:
+        return x
+    zeros_shape = list(x.shape)
+    zeros_shape[axis] = n
+    zeros = np.zeros(zeros_shape, dtype=x.dtype)
+    ext = np.concatenate((zeros, x, zeros), axis=axis)
+    return ext
+
+
+def _validate_fs(fs, allow_none=True):
+    """
+    Check if the given sampling frequency is a scalar and raises an exception
+    otherwise. If allow_none is False, also raises an exception for none
+    sampling rates. Returns the sampling frequency as float or none if the
+    input is none.
+    """
+    if fs is None:
+        if not allow_none:
+            raise ValueError("Sampling frequency can not be none.")
+    else:  # should be float
+        if not np.isscalar(fs):
+            raise ValueError("Sampling frequency fs must be a single scalar.")
+        fs = float(fs)
+    return fs

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_czt.py

@@ -0,0 +1,575 @@
+# This program is public domain
+# Authors: Paul Kienzle, Nadav Horesh
+"""
+Chirp z-transform.
+
+We provide two interfaces to the chirp z-transform: an object interface
+which precalculates part of the transform and can be applied efficiently
+to many different data sets, and a functional interface which is applied
+only to the given data set.
+
+Transforms
+----------
+
+CZT : callable (x, axis=-1) -> array
+   Define a chirp z-transform that can be applied to different signals.
+ZoomFFT : callable (x, axis=-1) -> array
+   Define a Fourier transform on a range of frequencies.
+
+Functions
+---------
+
+czt : array
+   Compute the chirp z-transform for a signal.
+zoom_fft : array
+   Compute the Fourier transform on a range of frequencies.
+"""
+
+import cmath
+import numbers
+import numpy as np
+from numpy import pi, arange
+from scipy.fft import fft, ifft, next_fast_len
+
+__all__ = ['czt', 'zoom_fft', 'CZT', 'ZoomFFT', 'czt_points']
+
+
+def _validate_sizes(n, m):
+    if n < 1 or not isinstance(n, numbers.Integral):
+        raise ValueError('Invalid number of CZT data '
+                         f'points ({n}) specified. '
+                         'n must be positive and integer type.')
+
+    if m is None:
+        m = n
+    elif m < 1 or not isinstance(m, numbers.Integral):
+        raise ValueError('Invalid number of CZT output '
+                         f'points ({m}) specified. '
+                         'm must be positive and integer type.')
+
+    return m
+
+
+def czt_points(m, w=None, a=1+0j):
+    """
+    Return the points at which the chirp z-transform is computed.
+
+    Parameters
+    ----------
+    m : int
+        The number of points desired.
+    w : complex, optional
+        The ratio between points in each step.
+        Defaults to equally spaced points around the entire unit circle.
+    a : complex, optional
+        The starting point in the complex plane.  Default is 1+0j.
+
+    Returns
+    -------
+    out : ndarray
+        The points in the Z plane at which `CZT` samples the z-transform,
+        when called with arguments `m`, `w`, and `a`, as complex numbers.
+
+    See Also
+    --------
+    CZT : Class that creates a callable chirp z-transform function.
+    czt : Convenience function for quickly calculating CZT.
+
+    Examples
+    --------
+    Plot the points of a 16-point FFT:
+
+    >>> import numpy as np
+    >>> from scipy.signal import czt_points
+    >>> points = czt_points(16)
+    >>> import matplotlib.pyplot as plt
+    >>> plt.plot(points.real, points.imag, 'o')
+    >>> plt.gca().add_patch(plt.Circle((0,0), radius=1, fill=False, alpha=.3))
+    >>> plt.axis('equal')
+    >>> plt.show()
+
+    and a 91-point logarithmic spiral that crosses the unit circle:
+
+    >>> m, w, a = 91, 0.995*np.exp(-1j*np.pi*.05), 0.8*np.exp(1j*np.pi/6)
+    >>> points = czt_points(m, w, a)
+    >>> plt.plot(points.real, points.imag, 'o')
+    >>> plt.gca().add_patch(plt.Circle((0,0), radius=1, fill=False, alpha=.3))
+    >>> plt.axis('equal')
+    >>> plt.show()
+    """
+    m = _validate_sizes(1, m)
+
+    k = arange(m)
+
+    a = 1.0 * a  # at least float
+
+    if w is None:
+        # Nothing specified, default to FFT
+        return a * np.exp(2j * pi * k / m)
+    else:
+        # w specified
+        w = 1.0 * w  # at least float
+        return a * w**-k
+
+
+class CZT:
+    """
+    Create a callable chirp z-transform function.
+
+    Transform to compute the frequency response around a spiral.
+    Objects of this class are callables which can compute the
+    chirp z-transform on their inputs.  This object precalculates the constant
+    chirps used in the given transform.
+
+    Parameters
+    ----------
+    n : int
+        The size of the signal.
+    m : int, optional
+        The number of output points desired.  Default is `n`.
+    w : complex, optional
+        The ratio between points in each step.  This must be precise or the
+        accumulated error will degrade the tail of the output sequence.
+        Defaults to equally spaced points around the entire unit circle.
+    a : complex, optional
+        The starting point in the complex plane.  Default is 1+0j.
+
+    Returns
+    -------
+    f : CZT
+        Callable object ``f(x, axis=-1)`` for computing the chirp z-transform
+        on `x`.
+
+    See Also
+    --------
+    czt : Convenience function for quickly calculating CZT.
+    ZoomFFT : Class that creates a callable partial FFT function.
+
+    Notes
+    -----
+    The defaults are chosen such that ``f(x)`` is equivalent to
+    ``fft.fft(x)`` and, if ``m > len(x)``, that ``f(x, m)`` is equivalent to
+    ``fft.fft(x, m)``.
+
+    If `w` does not lie on the unit circle, then the transform will be
+    around a spiral with exponentially-increasing radius.  Regardless,
+    angle will increase linearly.
+
+    For transforms that do lie on the unit circle, accuracy is better when
+    using `ZoomFFT`, since any numerical error in `w` is
+    accumulated for long data lengths, drifting away from the unit circle.
+
+    The chirp z-transform can be faster than an equivalent FFT with
+    zero padding.  Try it with your own array sizes to see.
+
+    However, the chirp z-transform is considerably less precise than the
+    equivalent zero-padded FFT.
+
+    As this CZT is implemented using the Bluestein algorithm, it can compute
+    large prime-length Fourier transforms in O(N log N) time, rather than the
+    O(N**2) time required by the direct DFT calculation.  (`scipy.fft` also
+    uses Bluestein's algorithm'.)
+
+    (The name "chirp z-transform" comes from the use of a chirp in the
+    Bluestein algorithm.  It does not decompose signals into chirps, like
+    other transforms with "chirp" in the name.)
+
+    References
+    ----------
+    .. [1] Leo I. Bluestein, "A linear filtering approach to the computation
+           of the discrete Fourier transform," Northeast Electronics Research
+           and Engineering Meeting Record 10, 218-219 (1968).
+    .. [2] Rabiner, Schafer, and Rader, "The chirp z-transform algorithm and
+           its application," Bell Syst. Tech. J. 48, 1249-1292 (1969).
+
+    Examples
+    --------
+    Compute multiple prime-length FFTs:
+
+    >>> from scipy.signal import CZT
+    >>> import numpy as np
+    >>> a = np.random.rand(7)
+    >>> b = np.random.rand(7)
+    >>> c = np.random.rand(7)
+    >>> czt_7 = CZT(n=7)
+    >>> A = czt_7(a)
+    >>> B = czt_7(b)
+    >>> C = czt_7(c)
+
+    Display the points at which the FFT is calculated:
+
+    >>> czt_7.points()
+    array([ 1.00000000+0.j        ,  0.62348980+0.78183148j,
+           -0.22252093+0.97492791j, -0.90096887+0.43388374j,
+           -0.90096887-0.43388374j, -0.22252093-0.97492791j,
+            0.62348980-0.78183148j])
+    >>> import matplotlib.pyplot as plt
+    >>> plt.plot(czt_7.points().real, czt_7.points().imag, 'o')
+    >>> plt.gca().add_patch(plt.Circle((0,0), radius=1, fill=False, alpha=.3))
+    >>> plt.axis('equal')
+    >>> plt.show()
+    """
+
+    def __init__(self, n, m=None, w=None, a=1+0j):
+        m = _validate_sizes(n, m)
+
+        k = arange(max(m, n), dtype=np.min_scalar_type(-max(m, n)**2))
+
+        if w is None:
+            # Nothing specified, default to FFT-like
+            w = cmath.exp(-2j*pi/m)
+            wk2 = np.exp(-(1j * pi * ((k**2) % (2*m))) / m)
+        else:
+            # w specified
+            wk2 = w**(k**2/2.)
+
+        a = 1.0 * a  # at least float
+
+        self.w, self.a = w, a
+        self.m, self.n = m, n
+
+        nfft = next_fast_len(n + m - 1)
+        self._Awk2 = a**-k[:n] * wk2[:n]
+        self._nfft = nfft
+        self._Fwk2 = fft(1/np.hstack((wk2[n-1:0:-1], wk2[:m])), nfft)
+        self._wk2 = wk2[:m]
+        self._yidx = slice(n-1, n+m-1)
+
+    def __call__(self, x, *, axis=-1):
+        """
+        Calculate the chirp z-transform of a signal.
+
+        Parameters
+        ----------
+        x : array
+            The signal to transform.
+        axis : int, optional
+            Axis over which to compute the FFT. If not given, the last axis is
+            used.
+
+        Returns
+        -------
+        out : ndarray
+            An array of the same dimensions as `x`, but with the length of the
+            transformed axis set to `m`.
+        """
+        x = np.asarray(x)
+        if x.shape[axis] != self.n:
+            raise ValueError(f"CZT defined for length {self.n}, not "
+                             f"{x.shape[axis]}")
+        # Calculate transpose coordinates, to allow operation on any given axis
+        trnsp = np.arange(x.ndim)
+        trnsp[[axis, -1]] = [-1, axis]
+        x = x.transpose(*trnsp)
+        y = ifft(self._Fwk2 * fft(x*self._Awk2, self._nfft))
+        y = y[..., self._yidx] * self._wk2
+        return y.transpose(*trnsp)
+
+    def points(self):
+        """
+        Return the points at which the chirp z-transform is computed.
+        """
+        return czt_points(self.m, self.w, self.a)
+
+
+class ZoomFFT(CZT):
+    """
+    Create a callable zoom FFT transform function.
+
+    This is a specialization of the chirp z-transform (`CZT`) for a set of
+    equally-spaced frequencies around the unit circle, used to calculate a
+    section of the FFT more efficiently than calculating the entire FFT and
+    truncating.
+
+    Parameters
+    ----------
+    n : int
+        The size of the signal.
+    fn : array_like
+        A length-2 sequence [`f1`, `f2`] giving the frequency range, or a
+        scalar, for which the range [0, `fn`] is assumed.
+    m : int, optional
+        The number of points to evaluate.  Default is `n`.
+    fs : float, optional
+        The sampling frequency.  If ``fs=10`` represented 10 kHz, for example,
+        then `f1` and `f2` would also be given in kHz.
+        The default sampling frequency is 2, so `f1` and `f2` should be
+        in the range [0, 1] to keep the transform below the Nyquist
+        frequency.
+    endpoint : bool, optional
+        If True, `f2` is the last sample. Otherwise, it is not included.
+        Default is False.
+
+    Returns
+    -------
+    f : ZoomFFT
+        Callable object ``f(x, axis=-1)`` for computing the zoom FFT on `x`.
+
+    See Also
+    --------
+    zoom_fft : Convenience function for calculating a zoom FFT.
+
+    Notes
+    -----
+    The defaults are chosen such that ``f(x, 2)`` is equivalent to
+    ``fft.fft(x)`` and, if ``m > len(x)``, that ``f(x, 2, m)`` is equivalent to
+    ``fft.fft(x, m)``.
+
+    Sampling frequency is 1/dt, the time step between samples in the
+    signal `x`.  The unit circle corresponds to frequencies from 0 up
+    to the sampling frequency.  The default sampling frequency of 2
+    means that `f1`, `f2` values up to the Nyquist frequency are in the
+    range [0, 1). For `f1`, `f2` values expressed in radians, a sampling
+    frequency of 2*pi should be used.
+
+    Remember that a zoom FFT can only interpolate the points of the existing
+    FFT.  It cannot help to resolve two separate nearby frequencies.
+    Frequency resolution can only be increased by increasing acquisition
+    time.
+
+    These functions are implemented using Bluestein's algorithm (as is
+    `scipy.fft`). [2]_
+
+    References
+    ----------
+    .. [1] Steve Alan Shilling, "A study of the chirp z-transform and its
+           applications", pg 29 (1970)
+           https://krex.k-state.edu/dspace/bitstream/handle/2097/7844/LD2668R41972S43.pdf
+    .. [2] Leo I. Bluestein, "A linear filtering approach to the computation
+           of the discrete Fourier transform," Northeast Electronics Research
+           and Engineering Meeting Record 10, 218-219 (1968).
+
+    Examples
+    --------
+    To plot the transform results use something like the following:
+
+    >>> import numpy as np
+    >>> from scipy.signal import ZoomFFT
+    >>> t = np.linspace(0, 1, 1021)
+    >>> x = np.cos(2*np.pi*15*t) + np.sin(2*np.pi*17*t)
+    >>> f1, f2 = 5, 27
+    >>> transform = ZoomFFT(len(x), [f1, f2], len(x), fs=1021)
+    >>> X = transform(x)
+    >>> f = np.linspace(f1, f2, len(x))
+    >>> import matplotlib.pyplot as plt
+    >>> plt.plot(f, 20*np.log10(np.abs(X)))
+    >>> plt.show()
+    """
+
+    def __init__(self, n, fn, m=None, *, fs=2, endpoint=False):
+        m = _validate_sizes(n, m)
+
+        k = arange(max(m, n), dtype=np.min_scalar_type(-max(m, n)**2))
+
+        if np.size(fn) == 2:
+            f1, f2 = fn
+        elif np.size(fn) == 1:
+            f1, f2 = 0.0, fn
+        else:
+            raise ValueError('fn must be a scalar or 2-length sequence')
+
+        self.f1, self.f2, self.fs = f1, f2, fs
+
+        if endpoint:
+            scale = ((f2 - f1) * m) / (fs * (m - 1))
+        else:
+            scale = (f2 - f1) / fs
+        a = cmath.exp(2j * pi * f1/fs)
+        wk2 = np.exp(-(1j * pi * scale * k**2) / m)
+
+        self.w = cmath.exp(-2j*pi/m * scale)
+        self.a = a
+        self.m, self.n = m, n
+
+        ak = np.exp(-2j * pi * f1/fs * k[:n])
+        self._Awk2 = ak * wk2[:n]
+
+        nfft = next_fast_len(n + m - 1)
+        self._nfft = nfft
+        self._Fwk2 = fft(1/np.hstack((wk2[n-1:0:-1], wk2[:m])), nfft)
+        self._wk2 = wk2[:m]
+        self._yidx = slice(n-1, n+m-1)
+
+
+def czt(x, m=None, w=None, a=1+0j, *, axis=-1):
+    """
+    Compute the frequency response around a spiral in the Z plane.
+
+    Parameters
+    ----------
+    x : array
+        The signal to transform.
+    m : int, optional
+        The number of output points desired.  Default is the length of the
+        input data.
+    w : complex, optional
+        The ratio between points in each step.  This must be precise or the
+        accumulated error will degrade the tail of the output sequence.
+        Defaults to equally spaced points around the entire unit circle.
+    a : complex, optional
+        The starting point in the complex plane.  Default is 1+0j.
+    axis : int, optional
+        Axis over which to compute the FFT. If not given, the last axis is
+        used.
+
+    Returns
+    -------
+    out : ndarray
+        An array of the same dimensions as `x`, but with the length of the
+        transformed axis set to `m`.
+
+    See Also
+    --------
+    CZT : Class that creates a callable chirp z-transform function.
+    zoom_fft : Convenience function for partial FFT calculations.
+
+    Notes
+    -----
+    The defaults are chosen such that ``signal.czt(x)`` is equivalent to
+    ``fft.fft(x)`` and, if ``m > len(x)``, that ``signal.czt(x, m)`` is
+    equivalent to ``fft.fft(x, m)``.
+
+    If the transform needs to be repeated, use `CZT` to construct a
+    specialized transform function which can be reused without
+    recomputing constants.
+
+    An example application is in system identification, repeatedly evaluating
+    small slices of the z-transform of a system, around where a pole is
+    expected to exist, to refine the estimate of the pole's true location. [1]_
+
+    References
+    ----------
+    .. [1] Steve Alan Shilling, "A study of the chirp z-transform and its
+           applications", pg 20 (1970)
+           https://krex.k-state.edu/dspace/bitstream/handle/2097/7844/LD2668R41972S43.pdf
+
+    Examples
+    --------
+    Generate a sinusoid:
+
+    >>> import numpy as np
+    >>> f1, f2, fs = 8, 10, 200  # Hz
+    >>> t = np.linspace(0, 1, fs, endpoint=False)
+    >>> x = np.sin(2*np.pi*t*f2)
+    >>> import matplotlib.pyplot as plt
+    >>> plt.plot(t, x)
+    >>> plt.axis([0, 1, -1.1, 1.1])
+    >>> plt.show()
+
+    Its discrete Fourier transform has all of its energy in a single frequency
+    bin:
+
+    >>> from scipy.fft import rfft, rfftfreq
+    >>> from scipy.signal import czt, czt_points
+    >>> plt.plot(rfftfreq(fs, 1/fs), abs(rfft(x)))
+    >>> plt.margins(0, 0.1)
+    >>> plt.show()
+
+    However, if the sinusoid is logarithmically-decaying:
+
+    >>> x = np.exp(-t*f1) * np.sin(2*np.pi*t*f2)
+    >>> plt.plot(t, x)
+    >>> plt.axis([0, 1, -1.1, 1.1])
+    >>> plt.show()
+
+    the DFT will have spectral leakage:
+
+    >>> plt.plot(rfftfreq(fs, 1/fs), abs(rfft(x)))
+    >>> plt.margins(0, 0.1)
+    >>> plt.show()
+
+    While the DFT always samples the z-transform around the unit circle, the
+    chirp z-transform allows us to sample the Z-transform along any
+    logarithmic spiral, such as a circle with radius smaller than unity:
+
+    >>> M = fs // 2  # Just positive frequencies, like rfft
+    >>> a = np.exp(-f1/fs)  # Starting point of the circle, radius < 1
+    >>> w = np.exp(-1j*np.pi/M)  # "Step size" of circle
+    >>> points = czt_points(M + 1, w, a)  # M + 1 to include Nyquist
+    >>> plt.plot(points.real, points.imag, '.')
+    >>> plt.gca().add_patch(plt.Circle((0,0), radius=1, fill=False, alpha=.3))
+    >>> plt.axis('equal'); plt.axis([-1.05, 1.05, -0.05, 1.05])
+    >>> plt.show()
+
+    With the correct radius, this transforms the decaying sinusoid (and others
+    with the same decay rate) without spectral leakage:
+
+    >>> z_vals = czt(x, M + 1, w, a)  # Include Nyquist for comparison to rfft
+    >>> freqs = np.angle(points)*fs/(2*np.pi)  # angle = omega, radius = sigma
+    >>> plt.plot(freqs, abs(z_vals))
+    >>> plt.margins(0, 0.1)
+    >>> plt.show()
+    """
+    x = np.asarray(x)
+    transform = CZT(x.shape[axis], m=m, w=w, a=a)
+    return transform(x, axis=axis)
+
+
+def zoom_fft(x, fn, m=None, *, fs=2, endpoint=False, axis=-1):
+    """
+    Compute the DFT of `x` only for frequencies in range `fn`.
+
+    Parameters
+    ----------
+    x : array
+        The signal to transform.
+    fn : array_like
+        A length-2 sequence [`f1`, `f2`] giving the frequency range, or a
+        scalar, for which the range [0, `fn`] is assumed.
+    m : int, optional
+        The number of points to evaluate.  The default is the length of `x`.
+    fs : float, optional
+        The sampling frequency.  If ``fs=10`` represented 10 kHz, for example,
+        then `f1` and `f2` would also be given in kHz.
+        The default sampling frequency is 2, so `f1` and `f2` should be
+        in the range [0, 1] to keep the transform below the Nyquist
+        frequency.
+    endpoint : bool, optional
+        If True, `f2` is the last sample. Otherwise, it is not included.
+        Default is False.
+    axis : int, optional
+        Axis over which to compute the FFT. If not given, the last axis is
+        used.
+
+    Returns
+    -------
+    out : ndarray
+        The transformed signal.  The Fourier transform will be calculated
+        at the points f1, f1+df, f1+2df, ..., f2, where df=(f2-f1)/m.
+
+    See Also
+    --------
+    ZoomFFT : Class that creates a callable partial FFT function.
+
+    Notes
+    -----
+    The defaults are chosen such that ``signal.zoom_fft(x, 2)`` is equivalent
+    to ``fft.fft(x)`` and, if ``m > len(x)``, that ``signal.zoom_fft(x, 2, m)``
+    is equivalent to ``fft.fft(x, m)``.
+
+    To graph the magnitude of the resulting transform, use::
+
+        plot(linspace(f1, f2, m, endpoint=False), abs(zoom_fft(x, [f1, f2], m)))
+
+    If the transform needs to be repeated, use `ZoomFFT` to construct
+    a specialized transform function which can be reused without
+    recomputing constants.
+
+    Examples
+    --------
+    To plot the transform results use something like the following:
+
+    >>> import numpy as np
+    >>> from scipy.signal import zoom_fft
+    >>> t = np.linspace(0, 1, 1021)
+    >>> x = np.cos(2*np.pi*15*t) + np.sin(2*np.pi*17*t)
+    >>> f1, f2 = 5, 27
+    >>> X = zoom_fft(x, [f1, f2], len(x), fs=1021)
+    >>> f = np.linspace(f1, f2, len(x))
+    >>> import matplotlib.pyplot as plt
+    >>> plt.plot(f, 20*np.log10(np.abs(X)))
+    >>> plt.show()
+    """
+    x = np.asarray(x)
+    transform = ZoomFFT(x.shape[axis], fn, m=m, fs=fs, endpoint=endpoint)
+    return transform(x, axis=axis)

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_fir_filter_design.py

@@ -0,0 +1,1286 @@
+"""Functions for FIR filter design."""
+
+from math import ceil, log
+import operator
+import warnings
+from typing import Literal
+
+import numpy as np
+from numpy.fft import irfft, fft, ifft
+from scipy.special import sinc
+from scipy.linalg import (toeplitz, hankel, solve, LinAlgError, LinAlgWarning,
+                          lstsq)
+from scipy.signal._arraytools import _validate_fs
+
+from . import _sigtools
+
+__all__ = ['kaiser_beta', 'kaiser_atten', 'kaiserord',
+           'firwin', 'firwin2', 'remez', 'firls', 'minimum_phase']
+
+
+# Some notes on function parameters:
+#
+# `cutoff` and `width` are given as numbers between 0 and 1.  These are
+# relative frequencies, expressed as a fraction of the Nyquist frequency.
+# For example, if the Nyquist frequency is 2 KHz, then width=0.15 is a width
+# of 300 Hz.
+#
+# The `order` of a FIR filter is one less than the number of taps.
+# This is a potential source of confusion, so in the following code,
+# we will always use the number of taps as the parameterization of
+# the 'size' of the filter. The "number of taps" means the number
+# of coefficients, which is the same as the length of the impulse
+# response of the filter.
+
+
+def kaiser_beta(a):
+    """Compute the Kaiser parameter `beta`, given the attenuation `a`.
+
+    Parameters
+    ----------
+    a : float
+        The desired attenuation in the stopband and maximum ripple in
+        the passband, in dB.  This should be a *positive* number.
+
+    Returns
+    -------
+    beta : float
+        The `beta` parameter to be used in the formula for a Kaiser window.
+
+    References
+    ----------
+    Oppenheim, Schafer, "Discrete-Time Signal Processing", p.475-476.
+
+    Examples
+    --------
+    Suppose we want to design a lowpass filter, with 65 dB attenuation
+    in the stop band.  The Kaiser window parameter to be used in the
+    window method is computed by ``kaiser_beta(65)``:
+
+    >>> from scipy.signal import kaiser_beta
+    >>> kaiser_beta(65)
+    6.20426
+
+    """
+    if a > 50:
+        beta = 0.1102 * (a - 8.7)
+    elif a > 21:
+        beta = 0.5842 * (a - 21) ** 0.4 + 0.07886 * (a - 21)
+    else:
+        beta = 0.0
+    return beta
+
+
+def kaiser_atten(numtaps, width):
+    """Compute the attenuation of a Kaiser FIR filter.
+
+    Given the number of taps `N` and the transition width `width`, compute the
+    attenuation `a` in dB, given by Kaiser's formula:
+
+        a = 2.285 * (N - 1) * pi * width + 7.95
+
+    Parameters
+    ----------
+    numtaps : int
+        The number of taps in the FIR filter.
+    width : float
+        The desired width of the transition region between passband and
+        stopband (or, in general, at any discontinuity) for the filter,
+        expressed as a fraction of the Nyquist frequency.
+
+    Returns
+    -------
+    a : float
+        The attenuation of the ripple, in dB.
+
+    See Also
+    --------
+    kaiserord, kaiser_beta
+
+    Examples
+    --------
+    Suppose we want to design a FIR filter using the Kaiser window method
+    that will have 211 taps and a transition width of 9 Hz for a signal that
+    is sampled at 480 Hz. Expressed as a fraction of the Nyquist frequency,
+    the width is 9/(0.5*480) = 0.0375. The approximate attenuation (in dB)
+    is computed as follows:
+
+    >>> from scipy.signal import kaiser_atten
+    >>> kaiser_atten(211, 0.0375)
+    64.48099630593983
+
+    """
+    a = 2.285 * (numtaps - 1) * np.pi * width + 7.95
+    return a
+
+
+def kaiserord(ripple, width):
+    """
+    Determine the filter window parameters for the Kaiser window method.
+
+    The parameters returned by this function are generally used to create
+    a finite impulse response filter using the window method, with either
+    `firwin` or `firwin2`.
+
+    Parameters
+    ----------
+    ripple : float
+        Upper bound for the deviation (in dB) of the magnitude of the
+        filter's frequency response from that of the desired filter (not
+        including frequencies in any transition intervals). That is, if w
+        is the frequency expressed as a fraction of the Nyquist frequency,
+        A(w) is the actual frequency response of the filter and D(w) is the
+        desired frequency response, the design requirement is that::
+
+            abs(A(w) - D(w))) < 10**(-ripple/20)
+
+        for 0 <= w <= 1 and w not in a transition interval.
+    width : float
+        Width of transition region, normalized so that 1 corresponds to pi
+        radians / sample. That is, the frequency is expressed as a fraction
+        of the Nyquist frequency.
+
+    Returns
+    -------
+    numtaps : int
+        The length of the Kaiser window.
+    beta : float
+        The beta parameter for the Kaiser window.
+
+    See Also
+    --------
+    kaiser_beta, kaiser_atten
+
+    Notes
+    -----
+    There are several ways to obtain the Kaiser window:
+
+    - ``signal.windows.kaiser(numtaps, beta, sym=True)``
+    - ``signal.get_window(beta, numtaps)``
+    - ``signal.get_window(('kaiser', beta), numtaps)``
+
+    The empirical equations discovered by Kaiser are used.
+
+    References
+    ----------
+    Oppenheim, Schafer, "Discrete-Time Signal Processing", pp.475-476.
+
+    Examples
+    --------
+    We will use the Kaiser window method to design a lowpass FIR filter
+    for a signal that is sampled at 1000 Hz.
+
+    We want at least 65 dB rejection in the stop band, and in the pass
+    band the gain should vary no more than 0.5%.
+
+    We want a cutoff frequency of 175 Hz, with a transition between the
+    pass band and the stop band of 24 Hz. That is, in the band [0, 163],
+    the gain varies no more than 0.5%, and in the band [187, 500], the
+    signal is attenuated by at least 65 dB.
+
+    >>> import numpy as np
+    >>> from scipy.signal import kaiserord, firwin, freqz
+    >>> import matplotlib.pyplot as plt
+    >>> fs = 1000.0
+    >>> cutoff = 175
+    >>> width = 24
+
+    The Kaiser method accepts just a single parameter to control the pass
+    band ripple and the stop band rejection, so we use the more restrictive
+    of the two. In this case, the pass band ripple is 0.005, or 46.02 dB,
+    so we will use 65 dB as the design parameter.
+
+    Use `kaiserord` to determine the length of the filter and the
+    parameter for the Kaiser window.
+
+    >>> numtaps, beta = kaiserord(65, width/(0.5*fs))
+    >>> numtaps
+    167
+    >>> beta
+    6.20426
+
+    Use `firwin` to create the FIR filter.
+
+    >>> taps = firwin(numtaps, cutoff, window=('kaiser', beta),
+    ...               scale=False, fs=fs)
+
+    Compute the frequency response of the filter.  ``w`` is the array of
+    frequencies, and ``h`` is the corresponding complex array of frequency
+    responses.
+
+    >>> w, h = freqz(taps, worN=8000)
+    >>> w *= 0.5*fs/np.pi  # Convert w to Hz.
+
+    Compute the deviation of the magnitude of the filter's response from
+    that of the ideal lowpass filter. Values in the transition region are
+    set to ``nan``, so they won't appear in the plot.
+
+    >>> ideal = w < cutoff  # The "ideal" frequency response.
+    >>> deviation = np.abs(np.abs(h) - ideal)
+    >>> deviation[(w > cutoff - 0.5*width) & (w < cutoff + 0.5*width)] = np.nan
+
+    Plot the deviation. A close look at the left end of the stop band shows
+    that the requirement for 65 dB attenuation is violated in the first lobe
+    by about 0.125 dB. This is not unusual for the Kaiser window method.
+
+    >>> plt.plot(w, 20*np.log10(np.abs(deviation)))
+    >>> plt.xlim(0, 0.5*fs)
+    >>> plt.ylim(-90, -60)
+    >>> plt.grid(alpha=0.25)
+    >>> plt.axhline(-65, color='r', ls='--', alpha=0.3)
+    >>> plt.xlabel('Frequency (Hz)')
+    >>> plt.ylabel('Deviation from ideal (dB)')
+    >>> plt.title('Lowpass Filter Frequency Response')
+    >>> plt.show()
+
+    """
+    A = abs(ripple)  # in case somebody is confused as to what's meant
+    if A < 8:
+        # Formula for N is not valid in this range.
+        raise ValueError("Requested maximum ripple attenuation "
+                         f"{A:f} is too small for the Kaiser formula.")
+    beta = kaiser_beta(A)
+
+    # Kaiser's formula (as given in Oppenheim and Schafer) is for the filter
+    # order, so we have to add 1 to get the number of taps.
+    numtaps = (A - 7.95) / 2.285 / (np.pi * width) + 1
+
+    return int(ceil(numtaps)), beta
+
+
+def firwin(numtaps, cutoff, *, width=None, window='hamming', pass_zero=True,
+           scale=True, fs=None):
+    """
+    FIR filter design using the window method.
+
+    This function computes the coefficients of a finite impulse response
+    filter. The filter will have linear phase; it will be Type I if
+    `numtaps` is odd and Type II if `numtaps` is even.
+
+    Type II filters always have zero response at the Nyquist frequency, so a
+    ValueError exception is raised if firwin is called with `numtaps` even and
+    having a passband whose right end is at the Nyquist frequency.
+
+    Parameters
+    ----------
+    numtaps : int
+        Length of the filter (number of coefficients, i.e. the filter
+        order + 1).  `numtaps` must be odd if a passband includes the
+        Nyquist frequency.
+    cutoff : float or 1-D array_like
+        Cutoff frequency of filter (expressed in the same units as `fs`)
+        OR an array of cutoff frequencies (that is, band edges). In the 
+        former case, as a float, the cutoff frequency should correspond 
+        with the half-amplitude point, where the attenuation will be -6dB. 
+        In the latter case, the frequencies in `cutoff` should be positive 
+        and monotonically increasing between 0 and `fs/2`. The values 0 
+        and `fs/2` must not be included in `cutoff`. It should be noted 
+        that this is different than the behavior of `scipy.signal.iirdesign`, 
+        where the cutoff is the half-power point (-3dB).
+    width : float or None, optional
+        If `width` is not None, then assume it is the approximate width
+        of the transition region (expressed in the same units as `fs`)
+        for use in Kaiser FIR filter design. In this case, the `window`
+        argument is ignored.
+    window : string or tuple of string and parameter values, optional
+        Desired window to use. See `scipy.signal.get_window` for a list
+        of windows and required parameters.
+    pass_zero : {True, False, 'bandpass', 'lowpass', 'highpass', 'bandstop'}, optional
+        If True, the gain at the frequency 0 (i.e., the "DC gain") is 1.
+        If False, the DC gain is 0. Can also be a string argument for the
+        desired filter type (equivalent to ``btype`` in IIR design functions).
+
+        .. versionadded:: 1.3.0
+           Support for string arguments.
+    scale : bool, optional
+        Set to True to scale the coefficients so that the frequency
+        response is exactly unity at a certain frequency.
+        That frequency is either:
+
+        - 0 (DC) if the first passband starts at 0 (i.e. pass_zero
+          is True)
+        - `fs/2` (the Nyquist frequency) if the first passband ends at
+          `fs/2` (i.e the filter is a single band highpass filter);
+          center of first passband otherwise
+
+    fs : float, optional
+        The sampling frequency of the signal. Each frequency in `cutoff`
+        must be between 0 and ``fs/2``.  Default is 2.
+
+    Returns
+    -------
+    h : (numtaps,) ndarray
+        Coefficients of length `numtaps` FIR filter.
+
+    Raises
+    ------
+    ValueError
+        If any value in `cutoff` is less than or equal to 0 or greater
+        than or equal to ``fs/2``, if the values in `cutoff` are not strictly
+        monotonically increasing, or if `numtaps` is even but a passband
+        includes the Nyquist frequency.
+
+    See Also
+    --------
+    firwin2
+    firls
+    minimum_phase
+    remez
+
+    Examples
+    --------
+    Low-pass from 0 to f:
+
+    >>> from scipy import signal
+    >>> numtaps = 3
+    >>> f = 0.1
+    >>> signal.firwin(numtaps, f)
+    array([ 0.06799017,  0.86401967,  0.06799017])
+
+    Use a specific window function:
+
+    >>> signal.firwin(numtaps, f, window='nuttall')
+    array([  3.56607041e-04,   9.99286786e-01,   3.56607041e-04])
+
+    High-pass ('stop' from 0 to f):
+
+    >>> signal.firwin(numtaps, f, pass_zero=False)
+    array([-0.00859313,  0.98281375, -0.00859313])
+
+    Band-pass:
+
+    >>> f1, f2 = 0.1, 0.2
+    >>> signal.firwin(numtaps, [f1, f2], pass_zero=False)
+    array([ 0.06301614,  0.88770441,  0.06301614])
+
+    Band-stop:
+
+    >>> signal.firwin(numtaps, [f1, f2])
+    array([-0.00801395,  1.0160279 , -0.00801395])
+
+    Multi-band (passbands are [0, f1], [f2, f3] and [f4, 1]):
+
+    >>> f3, f4 = 0.3, 0.4
+    >>> signal.firwin(numtaps, [f1, f2, f3, f4])
+    array([-0.01376344,  1.02752689, -0.01376344])
+
+    Multi-band (passbands are [f1, f2] and [f3,f4]):
+
+    >>> signal.firwin(numtaps, [f1, f2, f3, f4], pass_zero=False)
+    array([ 0.04890915,  0.91284326,  0.04890915])
+
+    """
+    # The major enhancements to this function added in November 2010 were
+    # developed by Tom Krauss (see ticket #902).
+    fs = _validate_fs(fs, allow_none=True)
+    fs = 2 if fs is None else fs
+
+    nyq = 0.5 * fs
+
+    cutoff = np.atleast_1d(cutoff) / float(nyq)
+
+    # Check for invalid input.
+    if cutoff.ndim > 1:
+        raise ValueError("The cutoff argument must be at most "
+                         "one-dimensional.")
+    if cutoff.size == 0:
+        raise ValueError("At least one cutoff frequency must be given.")
+    if cutoff.min() <= 0 or cutoff.max() >= 1:
+        raise ValueError("Invalid cutoff frequency: frequencies must be "
+                         "greater than 0 and less than fs/2.")
+    if np.any(np.diff(cutoff) <= 0):
+        raise ValueError("Invalid cutoff frequencies: the frequencies "
+                         "must be strictly increasing.")
+
+    if width is not None:
+        # A width was given.  Find the beta parameter of the Kaiser window
+        # and set `window`.  This overrides the value of `window` passed in.
+        atten = kaiser_atten(numtaps, float(width) / nyq)
+        beta = kaiser_beta(atten)
+        window = ('kaiser', beta)
+
+    if isinstance(pass_zero, str):
+        if pass_zero in ('bandstop', 'lowpass'):
+            if pass_zero == 'lowpass':
+                if cutoff.size != 1:
+                    raise ValueError('cutoff must have one element if '
+                                     f'pass_zero=="lowpass", got {cutoff.shape}')
+            elif cutoff.size <= 1:
+                raise ValueError('cutoff must have at least two elements if '
+                                 f'pass_zero=="bandstop", got {cutoff.shape}')
+            pass_zero = True
+        elif pass_zero in ('bandpass', 'highpass'):
+            if pass_zero == 'highpass':
+                if cutoff.size != 1:
+                    raise ValueError('cutoff must have one element if '
+                                     f'pass_zero=="highpass", got {cutoff.shape}')
+            elif cutoff.size <= 1:
+                raise ValueError('cutoff must have at least two elements if '
+                                 f'pass_zero=="bandpass", got {cutoff.shape}')
+            pass_zero = False
+        else:
+            raise ValueError('pass_zero must be True, False, "bandpass", '
+                             '"lowpass", "highpass", or "bandstop", got '
+                             f'{pass_zero}')
+    pass_zero = bool(operator.index(pass_zero))  # ensure bool-like
+
+    pass_nyquist = bool(cutoff.size & 1) ^ pass_zero
+    if pass_nyquist and numtaps % 2 == 0:
+        raise ValueError("A filter with an even number of coefficients must "
+                         "have zero response at the Nyquist frequency.")
+
+    # Insert 0 and/or 1 at the ends of cutoff so that the length of cutoff
+    # is even, and each pair in cutoff corresponds to passband.
+    cutoff = np.hstack(([0.0] * pass_zero, cutoff, [1.0] * pass_nyquist))
+
+    # `bands` is a 2-D array; each row gives the left and right edges of
+    # a passband.
+    bands = cutoff.reshape(-1, 2)
+
+    # Build up the coefficients.
+    alpha = 0.5 * (numtaps - 1)
+    m = np.arange(0, numtaps) - alpha
+    h = 0
+    for left, right in bands:
+        h += right * sinc(right * m)
+        h -= left * sinc(left * m)
+
+    # Get and apply the window function.
+    from .windows import get_window
+    win = get_window(window, numtaps, fftbins=False)
+    h *= win
+
+    # Now handle scaling if desired.
+    if scale:
+        # Get the first passband.
+        left, right = bands[0]
+        if left == 0:
+            scale_frequency = 0.0
+        elif right == 1:
+            scale_frequency = 1.0
+        else:
+            scale_frequency = 0.5 * (left + right)
+        c = np.cos(np.pi * m * scale_frequency)
+        s = np.sum(h * c)
+        h /= s
+
+    return h
+
+
+# Original version of firwin2 from scipy ticket #457, submitted by "tash".
+#
+# Rewritten by Warren Weckesser, 2010.
+def firwin2(numtaps, freq, gain, *, nfreqs=None, window='hamming',
+            antisymmetric=False, fs=None):
+    """
+    FIR filter design using the window method.
+
+    From the given frequencies `freq` and corresponding gains `gain`,
+    this function constructs an FIR filter with linear phase and
+    (approximately) the given frequency response.
+
+    Parameters
+    ----------
+    numtaps : int
+        The number of taps in the FIR filter.  `numtaps` must be less than
+        `nfreqs`.
+    freq : array_like, 1-D
+        The frequency sampling points. Typically 0.0 to 1.0 with 1.0 being
+        Nyquist.  The Nyquist frequency is half `fs`.
+        The values in `freq` must be nondecreasing. A value can be repeated
+        once to implement a discontinuity. The first value in `freq` must
+        be 0, and the last value must be ``fs/2``. Values 0 and ``fs/2`` must
+        not be repeated.
+    gain : array_like
+        The filter gains at the frequency sampling points. Certain
+        constraints to gain values, depending on the filter type, are applied,
+        see Notes for details.
+    nfreqs : int, optional
+        The size of the interpolation mesh used to construct the filter.
+        For most efficient behavior, this should be a power of 2 plus 1
+        (e.g, 129, 257, etc). The default is one more than the smallest
+        power of 2 that is not less than `numtaps`. `nfreqs` must be greater
+        than `numtaps`.
+    window : string or (string, float) or float, or None, optional
+        Window function to use. Default is "hamming". See
+        `scipy.signal.get_window` for the complete list of possible values.
+        If None, no window function is applied.
+    antisymmetric : bool, optional
+        Whether resulting impulse response is symmetric/antisymmetric.
+        See Notes for more details.
+    fs : float, optional
+        The sampling frequency of the signal. Each frequency in `cutoff`
+        must be between 0 and ``fs/2``. Default is 2.
+
+    Returns
+    -------
+    taps : ndarray
+        The filter coefficients of the FIR filter, as a 1-D array of length
+        `numtaps`.
+
+    See Also
+    --------
+    firls
+    firwin
+    minimum_phase
+    remez
+
+    Notes
+    -----
+    From the given set of frequencies and gains, the desired response is
+    constructed in the frequency domain. The inverse FFT is applied to the
+    desired response to create the associated convolution kernel, and the
+    first `numtaps` coefficients of this kernel, scaled by `window`, are
+    returned.
+
+    The FIR filter will have linear phase. The type of filter is determined by
+    the value of 'numtaps` and `antisymmetric` flag.
+    There are four possible combinations:
+
+       - odd  `numtaps`, `antisymmetric` is False, type I filter is produced
+       - even `numtaps`, `antisymmetric` is False, type II filter is produced
+       - odd  `numtaps`, `antisymmetric` is True, type III filter is produced
+       - even `numtaps`, `antisymmetric` is True, type IV filter is produced
+
+    Magnitude response of all but type I filters are subjects to following
+    constraints:
+
+       - type II  -- zero at the Nyquist frequency
+       - type III -- zero at zero and Nyquist frequencies
+       - type IV  -- zero at zero frequency
+
+    .. versionadded:: 0.9.0
+
+    References
+    ----------
+    .. [1] Oppenheim, A. V. and Schafer, R. W., "Discrete-Time Signal
+       Processing", Prentice-Hall, Englewood Cliffs, New Jersey (1989).
+       (See, for example, Section 7.4.)
+
+    .. [2] Smith, Steven W., "The Scientist and Engineer's Guide to Digital
+       Signal Processing", Ch. 17. http://www.dspguide.com/ch17/1.htm
+
+    Examples
+    --------
+    A lowpass FIR filter with a response that is 1 on [0.0, 0.5], and
+    that decreases linearly on [0.5, 1.0] from 1 to 0:
+
+    >>> from scipy import signal
+    >>> taps = signal.firwin2(150, [0.0, 0.5, 1.0], [1.0, 1.0, 0.0])
+    >>> print(taps[72:78])
+    [-0.02286961 -0.06362756  0.57310236  0.57310236 -0.06362756 -0.02286961]
+
+    """
+    fs = _validate_fs(fs, allow_none=True)
+    fs = 2 if fs is None else fs
+    nyq = 0.5 * fs
+
+    if len(freq) != len(gain):
+        raise ValueError('freq and gain must be of same length.')
+
+    if nfreqs is not None and numtaps >= nfreqs:
+        raise ValueError(('ntaps must be less than nfreqs, but firwin2 was '
+                          'called with ntaps=%d and nfreqs=%s') %
+                         (numtaps, nfreqs))
+
+    if freq[0] != 0 or freq[-1] != nyq:
+        raise ValueError('freq must start with 0 and end with fs/2.')
+    d = np.diff(freq)
+    if (d < 0).any():
+        raise ValueError('The values in freq must be nondecreasing.')
+    d2 = d[:-1] + d[1:]
+    if (d2 == 0).any():
+        raise ValueError('A value in freq must not occur more than twice.')
+    if freq[1] == 0:
+        raise ValueError('Value 0 must not be repeated in freq')
+    if freq[-2] == nyq:
+        raise ValueError('Value fs/2 must not be repeated in freq')
+
+    if antisymmetric:
+        if numtaps % 2 == 0:
+            ftype = 4
+        else:
+            ftype = 3
+    else:
+        if numtaps % 2 == 0:
+            ftype = 2
+        else:
+            ftype = 1
+
+    if ftype == 2 and gain[-1] != 0.0:
+        raise ValueError("A Type II filter must have zero gain at the "
+                         "Nyquist frequency.")
+    elif ftype == 3 and (gain[0] != 0.0 or gain[-1] != 0.0):
+        raise ValueError("A Type III filter must have zero gain at zero "
+                         "and Nyquist frequencies.")
+    elif ftype == 4 and gain[0] != 0.0:
+        raise ValueError("A Type IV filter must have zero gain at zero "
+                         "frequency.")
+
+    if nfreqs is None:
+        nfreqs = 1 + 2 ** int(ceil(log(numtaps, 2)))
+
+    if (d == 0).any():
+        # Tweak any repeated values in freq so that interp works.
+        freq = np.array(freq, copy=True)
+        eps = np.finfo(float).eps * nyq
+        for k in range(len(freq) - 1):
+            if freq[k] == freq[k + 1]:
+                freq[k] = freq[k] - eps
+                freq[k + 1] = freq[k + 1] + eps
+        # Check if freq is strictly increasing after tweak
+        d = np.diff(freq)
+        if (d <= 0).any():
+            raise ValueError("freq cannot contain numbers that are too close "
+                             "(within eps * (fs/2): "
+                             f"{eps}) to a repeated value")
+
+    # Linearly interpolate the desired response on a uniform mesh `x`.
+    x = np.linspace(0.0, nyq, nfreqs)
+    fx = np.interp(x, freq, gain)
+
+    # Adjust the phases of the coefficients so that the first `ntaps` of the
+    # inverse FFT are the desired filter coefficients.
+    shift = np.exp(-(numtaps - 1) / 2. * 1.j * np.pi * x / nyq)
+    if ftype > 2:
+        shift *= 1j
+
+    fx2 = fx * shift
+
+    # Use irfft to compute the inverse FFT.
+    out_full = irfft(fx2)
+
+    if window is not None:
+        # Create the window to apply to the filter coefficients.
+        from .windows import get_window
+        wind = get_window(window, numtaps, fftbins=False)
+    else:
+        wind = 1
+
+    # Keep only the first `numtaps` coefficients in `out`, and multiply by
+    # the window.
+    out = out_full[:numtaps] * wind
+
+    if ftype == 3:
+        out[out.size // 2] = 0.0
+
+    return out
+
+
+def remez(numtaps, bands, desired, *, weight=None, type='bandpass',
+          maxiter=25, grid_density=16, fs=None):
+    """
+    Calculate the minimax optimal filter using the Remez exchange algorithm.
+
+    Calculate the filter-coefficients for the finite impulse response
+    (FIR) filter whose transfer function minimizes the maximum error
+    between the desired gain and the realized gain in the specified
+    frequency bands using the Remez exchange algorithm.
+
+    Parameters
+    ----------
+    numtaps : int
+        The desired number of taps in the filter. The number of taps is
+        the number of terms in the filter, or the filter order plus one.
+    bands : array_like
+        A monotonic sequence containing the band edges.
+        All elements must be non-negative and less than half the sampling
+        frequency as given by `fs`.
+    desired : array_like
+        A sequence half the size of bands containing the desired gain
+        in each of the specified bands.
+    weight : array_like, optional
+        A relative weighting to give to each band region. The length of
+        `weight` has to be half the length of `bands`.
+    type : {'bandpass', 'differentiator', 'hilbert'}, optional
+        The type of filter:
+
+          * 'bandpass' : flat response in bands. This is the default.
+
+          * 'differentiator' : frequency proportional response in bands.
+
+          * 'hilbert' : filter with odd symmetry, that is, type III
+                        (for even order) or type IV (for odd order)
+                        linear phase filters.
+
+    maxiter : int, optional
+        Maximum number of iterations of the algorithm. Default is 25.
+    grid_density : int, optional
+        Grid density. The dense grid used in `remez` is of size
+        ``(numtaps + 1) * grid_density``. Default is 16.
+    fs : float, optional
+        The sampling frequency of the signal.  Default is 1.
+
+    Returns
+    -------
+    out : ndarray
+        A rank-1 array containing the coefficients of the optimal
+        (in a minimax sense) filter.
+
+    See Also
+    --------
+    firls
+    firwin
+    firwin2
+    minimum_phase
+
+    References
+    ----------
+    .. [1] J. H. McClellan and T. W. Parks, "A unified approach to the
+           design of optimum FIR linear phase digital filters",
+           IEEE Trans. Circuit Theory, vol. CT-20, pp. 697-701, 1973.
+    .. [2] J. H. McClellan, T. W. Parks and L. R. Rabiner, "A Computer
+           Program for Designing Optimum FIR Linear Phase Digital
+           Filters", IEEE Trans. Audio Electroacoust., vol. AU-21,
+           pp. 506-525, 1973.
+
+    Examples
+    --------
+    In these examples, `remez` is used to design low-pass, high-pass,
+    band-pass and band-stop filters.  The parameters that define each filter
+    are the filter order, the band boundaries, the transition widths of the
+    boundaries, the desired gains in each band, and the sampling frequency.
+
+    We'll use a sample frequency of 22050 Hz in all the examples.  In each
+    example, the desired gain in each band is either 0 (for a stop band)
+    or 1 (for a pass band).
+
+    `freqz` is used to compute the frequency response of each filter, and
+    the utility function ``plot_response`` defined below is used to plot
+    the response.
+
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> import matplotlib.pyplot as plt
+
+    >>> fs = 22050   # Sample rate, Hz
+
+    >>> def plot_response(w, h, title):
+    ...     "Utility function to plot response functions"
+    ...     fig = plt.figure()
+    ...     ax = fig.add_subplot(111)
+    ...     ax.plot(w, 20*np.log10(np.abs(h)))
+    ...     ax.set_ylim(-40, 5)
+    ...     ax.grid(True)
+    ...     ax.set_xlabel('Frequency (Hz)')
+    ...     ax.set_ylabel('Gain (dB)')
+    ...     ax.set_title(title)
+
+    The first example is a low-pass filter, with cutoff frequency 8 kHz.
+    The filter length is 325, and the transition width from pass to stop
+    is 100 Hz.
+
+    >>> cutoff = 8000.0    # Desired cutoff frequency, Hz
+    >>> trans_width = 100  # Width of transition from pass to stop, Hz
+    >>> numtaps = 325      # Size of the FIR filter.
+    >>> taps = signal.remez(numtaps, [0, cutoff, cutoff + trans_width, 0.5*fs],
+    ...                     [1, 0], fs=fs)
+    >>> w, h = signal.freqz(taps, [1], worN=2000, fs=fs)
+    >>> plot_response(w, h, "Low-pass Filter")
+    >>> plt.show()
+
+    This example shows a high-pass filter:
+
+    >>> cutoff = 2000.0    # Desired cutoff frequency, Hz
+    >>> trans_width = 250  # Width of transition from pass to stop, Hz
+    >>> numtaps = 125      # Size of the FIR filter.
+    >>> taps = signal.remez(numtaps, [0, cutoff - trans_width, cutoff, 0.5*fs],
+    ...                     [0, 1], fs=fs)
+    >>> w, h = signal.freqz(taps, [1], worN=2000, fs=fs)
+    >>> plot_response(w, h, "High-pass Filter")
+    >>> plt.show()
+
+    This example shows a band-pass filter with a pass-band from 2 kHz to
+    5 kHz.  The transition width is 260 Hz and the length of the filter
+    is 63, which is smaller than in the other examples:
+
+    >>> band = [2000, 5000]  # Desired pass band, Hz
+    >>> trans_width = 260    # Width of transition from pass to stop, Hz
+    >>> numtaps = 63         # Size of the FIR filter.
+    >>> edges = [0, band[0] - trans_width, band[0], band[1],
+    ...          band[1] + trans_width, 0.5*fs]
+    >>> taps = signal.remez(numtaps, edges, [0, 1, 0], fs=fs)
+    >>> w, h = signal.freqz(taps, [1], worN=2000, fs=fs)
+    >>> plot_response(w, h, "Band-pass Filter")
+    >>> plt.show()
+
+    The low order leads to higher ripple and less steep transitions.
+
+    The next example shows a band-stop filter.
+
+    >>> band = [6000, 8000]  # Desired stop band, Hz
+    >>> trans_width = 200    # Width of transition from pass to stop, Hz
+    >>> numtaps = 175        # Size of the FIR filter.
+    >>> edges = [0, band[0] - trans_width, band[0], band[1],
+    ...          band[1] + trans_width, 0.5*fs]
+    >>> taps = signal.remez(numtaps, edges, [1, 0, 1], fs=fs)
+    >>> w, h = signal.freqz(taps, [1], worN=2000, fs=fs)
+    >>> plot_response(w, h, "Band-stop Filter")
+    >>> plt.show()
+
+    """
+    fs = _validate_fs(fs, allow_none=True)
+    fs = 1.0 if fs is None else fs
+
+    # Convert type
+    try:
+        tnum = {'bandpass': 1, 'differentiator': 2, 'hilbert': 3}[type]
+    except KeyError as e:
+        raise ValueError("Type must be 'bandpass', 'differentiator', "
+                         "or 'hilbert'") from e
+
+    # Convert weight
+    if weight is None:
+        weight = [1] * len(desired)
+
+    bands = np.asarray(bands).copy()
+    return _sigtools._remez(numtaps, bands, desired, weight, tnum, fs,
+                            maxiter, grid_density)
+
+
+def firls(numtaps, bands, desired, *, weight=None, fs=None):
+    """
+    FIR filter design using least-squares error minimization.
+
+    Calculate the filter coefficients for the linear-phase finite
+    impulse response (FIR) filter which has the best approximation
+    to the desired frequency response described by `bands` and
+    `desired` in the least squares sense (i.e., the integral of the
+    weighted mean-squared error within the specified bands is
+    minimized).
+
+    Parameters
+    ----------
+    numtaps : int
+        The number of taps in the FIR filter. `numtaps` must be odd.
+    bands : array_like
+        A monotonic nondecreasing sequence containing the band edges in
+        Hz. All elements must be non-negative and less than or equal to
+        the Nyquist frequency given by `nyq`. The bands are specified as
+        frequency pairs, thus, if using a 1D array, its length must be
+        even, e.g., `np.array([0, 1, 2, 3, 4, 5])`. Alternatively, the
+        bands can be specified as an nx2 sized 2D array, where n is the
+        number of bands, e.g, `np.array([[0, 1], [2, 3], [4, 5]])`.
+    desired : array_like
+        A sequence the same size as `bands` containing the desired gain
+        at the start and end point of each band.
+    weight : array_like, optional
+        A relative weighting to give to each band region when solving
+        the least squares problem. `weight` has to be half the size of
+        `bands`.
+    fs : float, optional
+        The sampling frequency of the signal. Each frequency in `bands`
+        must be between 0 and ``fs/2`` (inclusive). Default is 2.
+
+    Returns
+    -------
+    coeffs : ndarray
+        Coefficients of the optimal (in a least squares sense) FIR filter.
+
+    See Also
+    --------
+    firwin
+    firwin2
+    minimum_phase
+    remez
+
+    Notes
+    -----
+    This implementation follows the algorithm given in [1]_.
+    As noted there, least squares design has multiple advantages:
+
+        1. Optimal in a least-squares sense.
+        2. Simple, non-iterative method.
+        3. The general solution can obtained by solving a linear
+           system of equations.
+        4. Allows the use of a frequency dependent weighting function.
+
+    This function constructs a Type I linear phase FIR filter, which
+    contains an odd number of `coeffs` satisfying for :math:`n < numtaps`:
+
+    .. math:: coeffs(n) = coeffs(numtaps - 1 - n)
+
+    The odd number of coefficients and filter symmetry avoid boundary
+    conditions that could otherwise occur at the Nyquist and 0 frequencies
+    (e.g., for Type II, III, or IV variants).
+
+    .. versionadded:: 0.18
+
+    References
+    ----------
+    .. [1] Ivan Selesnick, Linear-Phase Fir Filter Design By Least Squares.
+           OpenStax CNX. Aug 9, 2005.
+           https://eeweb.engineering.nyu.edu/iselesni/EL713/firls/firls.pdf
+
+    Examples
+    --------
+    We want to construct a band-pass filter. Note that the behavior in the
+    frequency ranges between our stop bands and pass bands is unspecified,
+    and thus may overshoot depending on the parameters of our filter:
+
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> import matplotlib.pyplot as plt
+    >>> fig, axs = plt.subplots(2)
+    >>> fs = 10.0  # Hz
+    >>> desired = (0, 0, 1, 1, 0, 0)
+    >>> for bi, bands in enumerate(((0, 1, 2, 3, 4, 5), (0, 1, 2, 4, 4.5, 5))):
+    ...     fir_firls = signal.firls(73, bands, desired, fs=fs)
+    ...     fir_remez = signal.remez(73, bands, desired[::2], fs=fs)
+    ...     fir_firwin2 = signal.firwin2(73, bands, desired, fs=fs)
+    ...     hs = list()
+    ...     ax = axs[bi]
+    ...     for fir in (fir_firls, fir_remez, fir_firwin2):
+    ...         freq, response = signal.freqz(fir)
+    ...         hs.append(ax.semilogy(0.5*fs*freq/np.pi, np.abs(response))[0])
+    ...     for band, gains in zip(zip(bands[::2], bands[1::2]),
+    ...                            zip(desired[::2], desired[1::2])):
+    ...         ax.semilogy(band, np.maximum(gains, 1e-7), 'k--', linewidth=2)
+    ...     if bi == 0:
+    ...         ax.legend(hs, ('firls', 'remez', 'firwin2'),
+    ...                   loc='lower center', frameon=False)
+    ...     else:
+    ...         ax.set_xlabel('Frequency (Hz)')
+    ...     ax.grid(True)
+    ...     ax.set(title='Band-pass %d-%d Hz' % bands[2:4], ylabel='Magnitude')
+    ...
+    >>> fig.tight_layout()
+    >>> plt.show()
+
+    """
+    fs = _validate_fs(fs, allow_none=True)
+    fs = 2 if fs is None else fs
+    nyq = 0.5 * fs
+
+    numtaps = int(numtaps)
+    if numtaps % 2 == 0 or numtaps < 1:
+        raise ValueError("numtaps must be odd and >= 1")
+    M = (numtaps-1) // 2
+
+    # normalize bands 0->1 and make it 2 columns
+    nyq = float(nyq)
+    if nyq <= 0:
+        raise ValueError(f'nyq must be positive, got {nyq} <= 0.')
+    bands = np.asarray(bands).flatten() / nyq
+    if len(bands) % 2 != 0:
+        raise ValueError("bands must contain frequency pairs.")
+    if (bands < 0).any() or (bands > 1).any():
+        raise ValueError("bands must be between 0 and 1 relative to Nyquist")
+    bands.shape = (-1, 2)
+
+    # check remaining params
+    desired = np.asarray(desired).flatten()
+    if bands.size != desired.size:
+        raise ValueError(
+            f"desired must have one entry per frequency, got {desired.size} "
+            f"gains for {bands.size} frequencies."
+        )
+    desired.shape = (-1, 2)
+    if (np.diff(bands) <= 0).any() or (np.diff(bands[:, 0]) < 0).any():
+        raise ValueError("bands must be monotonically nondecreasing and have "
+                         "width > 0.")
+    if (bands[:-1, 1] > bands[1:, 0]).any():
+        raise ValueError("bands must not overlap.")
+    if (desired < 0).any():
+        raise ValueError("desired must be non-negative.")
+    if weight is None:
+        weight = np.ones(len(desired))
+    weight = np.asarray(weight).flatten()
+    if len(weight) != len(desired):
+        raise ValueError("weight must be the same size as the number of "
+                         f"band pairs ({len(bands)}).")
+    if (weight < 0).any():
+        raise ValueError("weight must be non-negative.")
+
+    # Set up the linear matrix equation to be solved, Qa = b
+
+    # We can express Q(k,n) = 0.5 Q1(k,n) + 0.5 Q2(k,n)
+    # where Q1(k,n)=q(k-n) and Q2(k,n)=q(k+n), i.e. a Toeplitz plus Hankel.
+
+    # We omit the factor of 0.5 above, instead adding it during coefficient
+    # calculation.
+
+    # We also omit the 1/π from both Q and b equations, as they cancel
+    # during solving.
+
+    # We have that:
+    #     q(n) = 1/π ∫W(ω)cos(nω)dω (over 0->π)
+    # Using our normalization ω=πf and with a constant weight W over each
+    # interval f1->f2 we get:
+    #     q(n) = W∫cos(πnf)df (0->1) = Wf sin(πnf)/πnf
+    # integrated over each f1->f2 pair (i.e., value at f2 - value at f1).
+    n = np.arange(numtaps)[:, np.newaxis, np.newaxis]
+    q = np.dot(np.diff(np.sinc(bands * n) * bands, axis=2)[:, :, 0], weight)
+
+    # Now we assemble our sum of Toeplitz and Hankel
+    Q1 = toeplitz(q[:M+1])
+    Q2 = hankel(q[:M+1], q[M:])
+    Q = Q1 + Q2
+
+    # Now for b(n) we have that:
+    #     b(n) = 1/π ∫ W(ω)D(ω)cos(nω)dω (over 0->π)
+    # Using our normalization ω=πf and with a constant weight W over each
+    # interval and a linear term for D(ω) we get (over each f1->f2 interval):
+    #     b(n) = W ∫ (mf+c)cos(πnf)df
+    #          = f(mf+c)sin(πnf)/πnf + mf**2 cos(nπf)/(πnf)**2
+    # integrated over each f1->f2 pair (i.e., value at f2 - value at f1).
+    n = n[:M + 1]  # only need this many coefficients here
+    # Choose m and c such that we are at the start and end weights
+    m = (np.diff(desired, axis=1) / np.diff(bands, axis=1))
+    c = desired[:, [0]] - bands[:, [0]] * m
+    b = bands * (m*bands + c) * np.sinc(bands * n)
+    # Use L'Hospital's rule here for cos(nπf)/(πnf)**2 @ n=0
+    b[0] -= m * bands * bands / 2.
+    b[1:] += m * np.cos(n[1:] * np.pi * bands) / (np.pi * n[1:]) ** 2
+    b = np.dot(np.diff(b, axis=2)[:, :, 0], weight)
+
+    # Now we can solve the equation
+    try:  # try the fast way
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter('always')
+            a = solve(Q, b, assume_a="pos", check_finite=False)
+        for ww in w:
+            if (ww.category == LinAlgWarning and
+                    str(ww.message).startswith('Ill-conditioned matrix')):
+                raise LinAlgError(str(ww.message))
+    except LinAlgError:  # in case Q is rank deficient
+        # This is faster than pinvh, even though we don't explicitly use
+        # the symmetry here. gelsy was faster than gelsd and gelss in
+        # some non-exhaustive tests.
+        a = lstsq(Q, b, lapack_driver='gelsy')[0]
+
+    # make coefficients symmetric (linear phase)
+    coeffs = np.hstack((a[:0:-1], 2 * a[0], a[1:]))
+    return coeffs
+
+
+def _dhtm(mag):
+    """Compute the modified 1-D discrete Hilbert transform
+
+    Parameters
+    ----------
+    mag : ndarray
+        The magnitude spectrum. Should be 1-D with an even length, and
+        preferably a fast length for FFT/IFFT.
+    """
+    # Adapted based on code by Niranjan Damera-Venkata,
+    # Brian L. Evans and Shawn R. McCaslin (see refs for `minimum_phase`)
+    sig = np.zeros(len(mag))
+    # Leave Nyquist and DC at 0, knowing np.abs(fftfreq(N)[midpt]) == 0.5
+    midpt = len(mag) // 2
+    sig[1:midpt] = 1
+    sig[midpt+1:] = -1
+    # eventually if we want to support complex filters, we will need a
+    # np.abs() on the mag inside the log, and should remove the .real
+    recon = ifft(mag * np.exp(fft(sig * ifft(np.log(mag))))).real
+    return recon
+
+
+def minimum_phase(h: np.ndarray,
+                  method: Literal['homomorphic', 'hilbert'] = 'homomorphic',
+                  n_fft: int | None = None, *, half: bool = True) -> np.ndarray:
+    """Convert a linear-phase FIR filter to minimum phase
+
+    Parameters
+    ----------
+    h : array
+        Linear-phase FIR filter coefficients.
+    method : {'hilbert', 'homomorphic'}
+        The provided methods are:
+
+            'homomorphic' (default)
+                This method [4]_ [5]_ works best with filters with an
+                odd number of taps, and the resulting minimum phase filter
+                will have a magnitude response that approximates the square
+                root of the original filter's magnitude response using half
+                the number of taps when ``half=True`` (default), or the
+                original magnitude spectrum using the same number of taps
+                when ``half=False``.
+
+            'hilbert'
+                This method [1]_ is designed to be used with equiripple
+                filters (e.g., from `remez`) with unity or zero gain
+                regions.
+
+    n_fft : int
+        The number of points to use for the FFT. Should be at least a
+        few times larger than the signal length (see Notes).
+    half : bool
+        If ``True``, create a filter that is half the length of the original, with a
+        magnitude spectrum that is the square root of the original. If ``False``,
+        create a filter that is the same length as the original, with a magnitude
+        spectrum that is designed to match the original (only supported when
+        ``method='homomorphic'``).
+
+        .. versionadded:: 1.14.0
+
+    Returns
+    -------
+    h_minimum : array
+        The minimum-phase version of the filter, with length
+        ``(len(h) + 1) // 2`` when ``half is True`` or ``len(h)`` otherwise.
+
+    See Also
+    --------
+    firwin
+    firwin2
+    remez
+
+    Notes
+    -----
+    Both the Hilbert [1]_ or homomorphic [4]_ [5]_ methods require selection
+    of an FFT length to estimate the complex cepstrum of the filter.
+
+    In the case of the Hilbert method, the deviation from the ideal
+    spectrum ``epsilon`` is related to the number of stopband zeros
+    ``n_stop`` and FFT length ``n_fft`` as::
+
+        epsilon = 2. * n_stop / n_fft
+
+    For example, with 100 stopband zeros and a FFT length of 2048,
+    ``epsilon = 0.0976``. If we conservatively assume that the number of
+    stopband zeros is one less than the filter length, we can take the FFT
+    length to be the next power of 2 that satisfies ``epsilon=0.01`` as::
+
+        n_fft = 2 ** int(np.ceil(np.log2(2 * (len(h) - 1) / 0.01)))
+
+    This gives reasonable results for both the Hilbert and homomorphic
+    methods, and gives the value used when ``n_fft=None``.
+
+    Alternative implementations exist for creating minimum-phase filters,
+    including zero inversion [2]_ and spectral factorization [3]_ [4]_.
+    For more information, see `this DSPGuru page
+    <http://dspguru.com/dsp/howtos/how-to-design-minimum-phase-fir-filters>`__.
+
+    References
+    ----------
+    .. [1] N. Damera-Venkata and B. L. Evans, "Optimal design of real and
+           complex minimum phase digital FIR filters," Acoustics, Speech,
+           and Signal Processing, 1999. Proceedings., 1999 IEEE International
+           Conference on, Phoenix, AZ, 1999, pp. 1145-1148 vol.3.
+           :doi:`10.1109/ICASSP.1999.756179`
+    .. [2] X. Chen and T. W. Parks, "Design of optimal minimum phase FIR
+           filters by direct factorization," Signal Processing,
+           vol. 10, no. 4, pp. 369-383, Jun. 1986.
+    .. [3] T. Saramaki, "Finite Impulse Response Filter Design," in
+           Handbook for Digital Signal Processing, chapter 4,
+           New York: Wiley-Interscience, 1993.
+    .. [4] J. S. Lim, Advanced Topics in Signal Processing.
+           Englewood Cliffs, N.J.: Prentice Hall, 1988.
+    .. [5] A. V. Oppenheim, R. W. Schafer, and J. R. Buck,
+           "Discrete-Time Signal Processing," 3rd edition.
+           Upper Saddle River, N.J.: Pearson, 2009.
+
+    Examples
+    --------
+    Create an optimal linear-phase low-pass filter `h` with a transition band of
+    [0.2, 0.3] (assuming a Nyquist frequency of 1):
+
+    >>> import numpy as np
+    >>> from scipy.signal import remez, minimum_phase, freqz, group_delay
+    >>> import matplotlib.pyplot as plt
+    >>> freq = [0, 0.2, 0.3, 1.0]
+    >>> desired = [1, 0]
+    >>> h_linear = remez(151, freq, desired, fs=2)
+
+    Convert it to minimum phase:
+
+    >>> h_hil = minimum_phase(h_linear, method='hilbert')
+    >>> h_hom = minimum_phase(h_linear, method='homomorphic')
+    >>> h_hom_full = minimum_phase(h_linear, method='homomorphic', half=False)
+
+    Compare the impulse and frequency response of the four filters:
+
+    >>> fig0, ax0 = plt.subplots(figsize=(6, 3), tight_layout=True)
+    >>> fig1, axs = plt.subplots(3, sharex='all', figsize=(6, 6), tight_layout=True)
+    >>> ax0.set_title("Impulse response")
+    >>> ax0.set(xlabel='Samples', ylabel='Amplitude', xlim=(0, len(h_linear) - 1))
+    >>> axs[0].set_title("Frequency Response")
+    >>> axs[0].set(xlim=(0, .65), ylabel="Magnitude / dB")
+    >>> axs[1].set(ylabel="Phase / rad")
+    >>> axs[2].set(ylabel="Group Delay / samples", ylim=(-31, 81),
+    ...             xlabel='Normalized Frequency (Nyqist frequency: 1)')
+    >>> for h, lb in ((h_linear,   f'Linear ({len(h_linear)})'),
+    ...               (h_hil,      f'Min-Hilbert ({len(h_hil)})'),
+    ...               (h_hom,      f'Min-Homomorphic ({len(h_hom)})'),
+    ...               (h_hom_full, f'Min-Homom. Full ({len(h_hom_full)})')):
+    ...     w_H, H = freqz(h, fs=2)
+    ...     w_gd, gd = group_delay((h, 1), fs=2)
+    ...
+    ...     alpha = 1.0 if lb == 'linear' else 0.5  # full opacity for 'linear' line
+    ...     ax0.plot(h, '.-', alpha=alpha, label=lb)
+    ...     axs[0].plot(w_H, 20 * np.log10(np.abs(H)), alpha=alpha)
+    ...     axs[1].plot(w_H, np.unwrap(np.angle(H)), alpha=alpha, label=lb)
+    ...     axs[2].plot(w_gd, gd, alpha=alpha)
+    >>> ax0.grid(True)
+    >>> ax0.legend(title='Filter Phase (Order)')
+    >>> axs[1].legend(title='Filter Phase (Order)', loc='lower right')
+    >>> for ax_ in axs:  # shade transition band:
+    ...     ax_.axvspan(freq[1], freq[2], color='y', alpha=.25)
+    ...     ax_.grid(True)
+    >>> plt.show()
+
+    The impulse response and group delay plot depict the 75 sample delay of the linear
+    phase filter `h`. The phase should also be linear in the stop band--due to the small
+    magnitude, numeric noise dominates there. Furthermore, the plots show that the
+    minimum phase filters clearly show a reduced (negative) phase slope in the pass and
+    transition band. The plots also illustrate that the filter with parameters
+    ``method='homomorphic', half=False`` has same order and magnitude response as the
+    linear filter `h` whereas the other minimum phase filters have only half the order
+    and the square root  of the magnitude response.
+    """
+    h = np.asarray(h)
+    if np.iscomplexobj(h):
+        raise ValueError('Complex filters not supported')
+    if h.ndim != 1 or h.size <= 2:
+        raise ValueError('h must be 1-D and at least 2 samples long')
+    n_half = len(h) // 2
+    if not np.allclose(h[-n_half:][::-1], h[:n_half]):
+        warnings.warn('h does not appear to by symmetric, conversion may fail',
+                      RuntimeWarning, stacklevel=2)
+    if not isinstance(method, str) or method not in \
+            ('homomorphic', 'hilbert',):
+        raise ValueError(f'method must be "homomorphic" or "hilbert", got {method!r}')
+    if method == "hilbert" and not half:
+        raise ValueError("`half=False` is only supported when `method='homomorphic'`")
+    if n_fft is None:
+        n_fft = 2 ** int(np.ceil(np.log2(2 * (len(h) - 1) / 0.01)))
+    n_fft = int(n_fft)
+    if n_fft < len(h):
+        raise ValueError(f'n_fft must be at least len(h)=={len(h)}')
+    if method == 'hilbert':
+        w = np.arange(n_fft) * (2 * np.pi / n_fft * n_half)
+        H = np.real(fft(h, n_fft) * np.exp(1j * w))
+        dp = max(H) - 1
+        ds = 0 - min(H)
+        S = 4. / (np.sqrt(1+dp+ds) + np.sqrt(1-dp+ds)) ** 2
+        H += ds
+        H *= S
+        H = np.sqrt(H, out=H)
+        H += 1e-10  # ensure that the log does not explode
+        h_minimum = _dhtm(H)
+    else:  # method == 'homomorphic'
+        # zero-pad; calculate the DFT
+        h_temp = np.abs(fft(h, n_fft))
+        # take 0.25*log(|H|**2) = 0.5*log(|H|)
+        h_temp += 1e-7 * h_temp[h_temp > 0].min()  # don't let log blow up
+        np.log(h_temp, out=h_temp)
+        if half:  # halving of magnitude spectrum optional
+            h_temp *= 0.5
+        # IDFT
+        h_temp = ifft(h_temp).real
+        # multiply pointwise by the homomorphic filter
+        # lmin[n] = 2u[n] - d[n]
+        # i.e., double the positive frequencies and zero out the negative ones;
+        # Oppenheim+Shafer 3rd ed p991 eq13.42b and p1004 fig13.7
+        win = np.zeros(n_fft)
+        win[0] = 1
+        stop = n_fft // 2
+        win[1:stop] = 2
+        if n_fft % 2:
+            win[stop] = 1
+        h_temp *= win
+        h_temp = ifft(np.exp(fft(h_temp)))
+        h_minimum = h_temp.real
+    n_out = (n_half + len(h) % 2) if half else len(h)
+    return h_minimum[:n_out]

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_lti_conversion.py

@@ -0,0 +1,533 @@
+"""
+ltisys -- a collection of functions to convert linear time invariant systems
+from one representation to another.
+"""
+
+import numpy as np
+from numpy import (r_, eye, atleast_2d, poly, dot,
+                   asarray, zeros, array, outer)
+from scipy import linalg
+
+from ._filter_design import tf2zpk, zpk2tf, normalize
+
+
+__all__ = ['tf2ss', 'abcd_normalize', 'ss2tf', 'zpk2ss', 'ss2zpk',
+           'cont2discrete']
+
+
+def tf2ss(num, den):
+    r"""Transfer function to state-space representation.
+
+    Parameters
+    ----------
+    num, den : array_like
+        Sequences representing the coefficients of the numerator and
+        denominator polynomials, in order of descending degree. The
+        denominator needs to be at least as long as the numerator.
+
+    Returns
+    -------
+    A, B, C, D : ndarray
+        State space representation of the system, in controller canonical
+        form.
+
+    Examples
+    --------
+    Convert the transfer function:
+
+    .. math:: H(s) = \frac{s^2 + 3s + 3}{s^2 + 2s + 1}
+
+    >>> num = [1, 3, 3]
+    >>> den = [1, 2, 1]
+
+    to the state-space representation:
+
+    .. math::
+
+        \dot{\textbf{x}}(t) =
+        \begin{bmatrix} -2 & -1 \\ 1 & 0 \end{bmatrix} \textbf{x}(t) +
+        \begin{bmatrix} 1 \\ 0 \end{bmatrix} \textbf{u}(t) \\
+
+        \textbf{y}(t) = \begin{bmatrix} 1 & 2 \end{bmatrix} \textbf{x}(t) +
+        \begin{bmatrix} 1 \end{bmatrix} \textbf{u}(t)
+
+    >>> from scipy.signal import tf2ss
+    >>> A, B, C, D = tf2ss(num, den)
+    >>> A
+    array([[-2., -1.],
+           [ 1.,  0.]])
+    >>> B
+    array([[ 1.],
+           [ 0.]])
+    >>> C
+    array([[ 1.,  2.]])
+    >>> D
+    array([[ 1.]])
+    """
+    # Controller canonical state-space representation.
+    #  if M+1 = len(num) and K+1 = len(den) then we must have M <= K
+    #  states are found by asserting that X(s) = U(s) / D(s)
+    #  then Y(s) = N(s) * X(s)
+    #
+    #   A, B, C, and D follow quite naturally.
+    #
+    num, den = normalize(num, den)   # Strips zeros, checks arrays
+    nn = len(num.shape)
+    if nn == 1:
+        num = asarray([num], num.dtype)
+    M = num.shape[1]
+    K = len(den)
+    if M > K:
+        msg = "Improper transfer function. `num` is longer than `den`."
+        raise ValueError(msg)
+    if M == 0 or K == 0:  # Null system
+        return (array([], float), array([], float), array([], float),
+                array([], float))
+
+    # pad numerator to have same number of columns has denominator
+    num = np.hstack((np.zeros((num.shape[0], K - M), dtype=num.dtype), num))
+
+    if num.shape[-1] > 0:
+        D = atleast_2d(num[:, 0])
+
+    else:
+        # We don't assign it an empty array because this system
+        # is not 'null'. It just doesn't have a non-zero D
+        # matrix. Thus, it should have a non-zero shape so that
+        # it can be operated on by functions like 'ss2tf'
+        D = array([[0]], float)
+
+    if K == 1:
+        D = D.reshape(num.shape)
+
+        return (zeros((1, 1)), zeros((1, D.shape[1])),
+                zeros((D.shape[0], 1)), D)
+
+    frow = -array([den[1:]])
+    A = r_[frow, eye(K - 2, K - 1)]
+    B = eye(K - 1, 1)
+    C = num[:, 1:] - outer(num[:, 0], den[1:])
+    D = D.reshape((C.shape[0], B.shape[1]))
+
+    return A, B, C, D
+
+
+def _none_to_empty_2d(arg):
+    if arg is None:
+        return zeros((0, 0))
+    else:
+        return arg
+
+
+def _atleast_2d_or_none(arg):
+    if arg is not None:
+        return atleast_2d(arg)
+
+
+def _shape_or_none(M):
+    if M is not None:
+        return M.shape
+    else:
+        return (None,) * 2
+
+
+def _choice_not_none(*args):
+    for arg in args:
+        if arg is not None:
+            return arg
+
+
+def _restore(M, shape):
+    if M.shape == (0, 0):
+        return zeros(shape)
+    else:
+        if M.shape != shape:
+            raise ValueError("The input arrays have incompatible shapes.")
+        return M
+
+
+def abcd_normalize(A=None, B=None, C=None, D=None):
+    """Check state-space matrices and ensure they are 2-D.
+
+    If enough information on the system is provided, that is, enough
+    properly-shaped arrays are passed to the function, the missing ones
+    are built from this information, ensuring the correct number of
+    rows and columns. Otherwise a ValueError is raised.
+
+    Parameters
+    ----------
+    A, B, C, D : array_like, optional
+        State-space matrices. All of them are None (missing) by default.
+        See `ss2tf` for format.
+
+    Returns
+    -------
+    A, B, C, D : array
+        Properly shaped state-space matrices.
+
+    Raises
+    ------
+    ValueError
+        If not enough information on the system was provided.
+
+    """
+    A, B, C, D = map(_atleast_2d_or_none, (A, B, C, D))
+
+    MA, NA = _shape_or_none(A)
+    MB, NB = _shape_or_none(B)
+    MC, NC = _shape_or_none(C)
+    MD, ND = _shape_or_none(D)
+
+    p = _choice_not_none(MA, MB, NC)
+    q = _choice_not_none(NB, ND)
+    r = _choice_not_none(MC, MD)
+    if p is None or q is None or r is None:
+        raise ValueError("Not enough information on the system.")
+
+    A, B, C, D = map(_none_to_empty_2d, (A, B, C, D))
+    A = _restore(A, (p, p))
+    B = _restore(B, (p, q))
+    C = _restore(C, (r, p))
+    D = _restore(D, (r, q))
+
+    return A, B, C, D
+
+
+def ss2tf(A, B, C, D, input=0):
+    r"""State-space to transfer function.
+
+    A, B, C, D defines a linear state-space system with `p` inputs,
+    `q` outputs, and `n` state variables.
+
+    Parameters
+    ----------
+    A : array_like
+        State (or system) matrix of shape ``(n, n)``
+    B : array_like
+        Input matrix of shape ``(n, p)``
+    C : array_like
+        Output matrix of shape ``(q, n)``
+    D : array_like
+        Feedthrough (or feedforward) matrix of shape ``(q, p)``
+    input : int, optional
+        For multiple-input systems, the index of the input to use.
+
+    Returns
+    -------
+    num : 2-D ndarray
+        Numerator(s) of the resulting transfer function(s). `num` has one row
+        for each of the system's outputs. Each row is a sequence representation
+        of the numerator polynomial.
+    den : 1-D ndarray
+        Denominator of the resulting transfer function(s). `den` is a sequence
+        representation of the denominator polynomial.
+
+    Examples
+    --------
+    Convert the state-space representation:
+
+    .. math::
+
+        \dot{\textbf{x}}(t) =
+        \begin{bmatrix} -2 & -1 \\ 1 & 0 \end{bmatrix} \textbf{x}(t) +
+        \begin{bmatrix} 1 \\ 0 \end{bmatrix} \textbf{u}(t) \\
+
+        \textbf{y}(t) = \begin{bmatrix} 1 & 2 \end{bmatrix} \textbf{x}(t) +
+        \begin{bmatrix} 1 \end{bmatrix} \textbf{u}(t)
+
+    >>> A = [[-2, -1], [1, 0]]
+    >>> B = [[1], [0]]  # 2-D column vector
+    >>> C = [[1, 2]]    # 2-D row vector
+    >>> D = 1
+
+    to the transfer function:
+
+    .. math:: H(s) = \frac{s^2 + 3s + 3}{s^2 + 2s + 1}
+
+    >>> from scipy.signal import ss2tf
+    >>> ss2tf(A, B, C, D)
+    (array([[1., 3., 3.]]), array([ 1.,  2.,  1.]))
+    """
+    # transfer function is C (sI - A)**(-1) B + D
+
+    # Check consistency and make them all rank-2 arrays
+    A, B, C, D = abcd_normalize(A, B, C, D)
+
+    nout, nin = D.shape
+    if input >= nin:
+        raise ValueError("System does not have the input specified.")
+
+    # make SIMO from possibly MIMO system.
+    B = B[:, input:input + 1]
+    D = D[:, input:input + 1]
+
+    try:
+        den = poly(A)
+    except ValueError:
+        den = 1
+
+    if (B.size == 0) and (C.size == 0):
+        num = np.ravel(D)
+        if (D.size == 0) and (A.size == 0):
+            den = []
+        return num, den
+
+    num_states = A.shape[0]
+    type_test = A[:, 0] + B[:, 0] + C[0, :] + D + 0.0
+    num = np.empty((nout, num_states + 1), type_test.dtype)
+    for k in range(nout):
+        Ck = atleast_2d(C[k, :])
+        num[k] = poly(A - dot(B, Ck)) + (D[k] - 1) * den
+
+    return num, den
+
+
+def zpk2ss(z, p, k):
+    """Zero-pole-gain representation to state-space representation
+
+    Parameters
+    ----------
+    z, p : sequence
+        Zeros and poles.
+    k : float
+        System gain.
+
+    Returns
+    -------
+    A, B, C, D : ndarray
+        State space representation of the system, in controller canonical
+        form.
+
+    """
+    return tf2ss(*zpk2tf(z, p, k))
+
+
+def ss2zpk(A, B, C, D, input=0):
+    """State-space representation to zero-pole-gain representation.
+
+    A, B, C, D defines a linear state-space system with `p` inputs,
+    `q` outputs, and `n` state variables.
+
+    Parameters
+    ----------
+    A : array_like
+        State (or system) matrix of shape ``(n, n)``
+    B : array_like
+        Input matrix of shape ``(n, p)``
+    C : array_like
+        Output matrix of shape ``(q, n)``
+    D : array_like
+        Feedthrough (or feedforward) matrix of shape ``(q, p)``
+    input : int, optional
+        For multiple-input systems, the index of the input to use.
+
+    Returns
+    -------
+    z, p : sequence
+        Zeros and poles.
+    k : float
+        System gain.
+
+    """
+    return tf2zpk(*ss2tf(A, B, C, D, input=input))
+
+
+def cont2discrete(system, dt, method="zoh", alpha=None):
+    """
+    Transform a continuous to a discrete state-space system.
+
+    Parameters
+    ----------
+    system : a tuple describing the system or an instance of `lti`
+        The following gives the number of elements in the tuple and
+        the interpretation:
+
+            * 1: (instance of `lti`)
+            * 2: (num, den)
+            * 3: (zeros, poles, gain)
+            * 4: (A, B, C, D)
+
+    dt : float
+        The discretization time step.
+    method : str, optional
+        Which method to use:
+
+            * gbt: generalized bilinear transformation
+            * bilinear: Tustin's approximation ("gbt" with alpha=0.5)
+            * euler: Euler (or forward differencing) method ("gbt" with alpha=0)
+            * backward_diff: Backwards differencing ("gbt" with alpha=1.0)
+            * zoh: zero-order hold (default)
+            * foh: first-order hold (*versionadded: 1.3.0*)
+            * impulse: equivalent impulse response (*versionadded: 1.3.0*)
+
+    alpha : float within [0, 1], optional
+        The generalized bilinear transformation weighting parameter, which
+        should only be specified with method="gbt", and is ignored otherwise
+
+    Returns
+    -------
+    sysd : tuple containing the discrete system
+        Based on the input type, the output will be of the form
+
+        * (num, den, dt)   for transfer function input
+        * (zeros, poles, gain, dt)   for zeros-poles-gain input
+        * (A, B, C, D, dt) for state-space system input
+
+    Notes
+    -----
+    By default, the routine uses a Zero-Order Hold (zoh) method to perform
+    the transformation. Alternatively, a generalized bilinear transformation
+    may be used, which includes the common Tustin's bilinear approximation,
+    an Euler's method technique, or a backwards differencing technique.
+
+    The Zero-Order Hold (zoh) method is based on [1]_, the generalized bilinear
+    approximation is based on [2]_ and [3]_, the First-Order Hold (foh) method
+    is based on [4]_.
+
+    References
+    ----------
+    .. [1] https://en.wikipedia.org/wiki/Discretization#Discretization_of_linear_state_space_models
+
+    .. [2] http://techteach.no/publications/discretetime_signals_systems/discrete.pdf
+
+    .. [3] G. Zhang, X. Chen, and T. Chen, Digital redesign via the generalized
+        bilinear transformation, Int. J. Control, vol. 82, no. 4, pp. 741-754,
+        2009.
+        (https://www.mypolyuweb.hk/~magzhang/Research/ZCC09_IJC.pdf)
+
+    .. [4] G. F. Franklin, J. D. Powell, and M. L. Workman, Digital control
+        of dynamic systems, 3rd ed. Menlo Park, Calif: Addison-Wesley,
+        pp. 204-206, 1998.
+
+    Examples
+    --------
+    We can transform a continuous state-space system to a discrete one:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.signal import cont2discrete, lti, dlti, dstep
+
+    Define a continuous state-space system.
+
+    >>> A = np.array([[0, 1],[-10., -3]])
+    >>> B = np.array([[0],[10.]])
+    >>> C = np.array([[1., 0]])
+    >>> D = np.array([[0.]])
+    >>> l_system = lti(A, B, C, D)
+    >>> t, x = l_system.step(T=np.linspace(0, 5, 100))
+    >>> fig, ax = plt.subplots()
+    >>> ax.plot(t, x, label='Continuous', linewidth=3)
+
+    Transform it to a discrete state-space system using several methods.
+
+    >>> dt = 0.1
+    >>> for method in ['zoh', 'bilinear', 'euler', 'backward_diff', 'foh', 'impulse']:
+    ...    d_system = cont2discrete((A, B, C, D), dt, method=method)
+    ...    s, x_d = dstep(d_system)
+    ...    ax.step(s, np.squeeze(x_d), label=method, where='post')
+    >>> ax.axis([t[0], t[-1], x[0], 1.4])
+    >>> ax.legend(loc='best')
+    >>> fig.tight_layout()
+    >>> plt.show()
+
+    """
+    if len(system) == 1:
+        return system.to_discrete()
+    if len(system) == 2:
+        sysd = cont2discrete(tf2ss(system[0], system[1]), dt, method=method,
+                             alpha=alpha)
+        return ss2tf(sysd[0], sysd[1], sysd[2], sysd[3]) + (dt,)
+    elif len(system) == 3:
+        sysd = cont2discrete(zpk2ss(system[0], system[1], system[2]), dt,
+                             method=method, alpha=alpha)
+        return ss2zpk(sysd[0], sysd[1], sysd[2], sysd[3]) + (dt,)
+    elif len(system) == 4:
+        a, b, c, d = system
+    else:
+        raise ValueError("First argument must either be a tuple of 2 (tf), "
+                         "3 (zpk), or 4 (ss) arrays.")
+
+    if method == 'gbt':
+        if alpha is None:
+            raise ValueError("Alpha parameter must be specified for the "
+                             "generalized bilinear transform (gbt) method")
+        elif alpha < 0 or alpha > 1:
+            raise ValueError("Alpha parameter must be within the interval "
+                             "[0,1] for the gbt method")
+
+    if method == 'gbt':
+        # This parameter is used repeatedly - compute once here
+        ima = np.eye(a.shape[0]) - alpha*dt*a
+        ad = linalg.solve(ima, np.eye(a.shape[0]) + (1.0-alpha)*dt*a)
+        bd = linalg.solve(ima, dt*b)
+
+        # Similarly solve for the output equation matrices
+        cd = linalg.solve(ima.transpose(), c.transpose())
+        cd = cd.transpose()
+        dd = d + alpha*np.dot(c, bd)
+
+    elif method == 'bilinear' or method == 'tustin':
+        return cont2discrete(system, dt, method="gbt", alpha=0.5)
+
+    elif method == 'euler' or method == 'forward_diff':
+        return cont2discrete(system, dt, method="gbt", alpha=0.0)
+
+    elif method == 'backward_diff':
+        return cont2discrete(system, dt, method="gbt", alpha=1.0)
+
+    elif method == 'zoh':
+        # Build an exponential matrix
+        em_upper = np.hstack((a, b))
+
+        # Need to stack zeros under the a and b matrices
+        em_lower = np.hstack((np.zeros((b.shape[1], a.shape[0])),
+                              np.zeros((b.shape[1], b.shape[1]))))
+
+        em = np.vstack((em_upper, em_lower))
+        ms = linalg.expm(dt * em)
+
+        # Dispose of the lower rows
+        ms = ms[:a.shape[0], :]
+
+        ad = ms[:, 0:a.shape[1]]
+        bd = ms[:, a.shape[1]:]
+
+        cd = c
+        dd = d
+
+    elif method == 'foh':
+        # Size parameters for convenience
+        n = a.shape[0]
+        m = b.shape[1]
+
+        # Build an exponential matrix similar to 'zoh' method
+        em_upper = linalg.block_diag(np.block([a, b]) * dt, np.eye(m))
+        em_lower = zeros((m, n + 2 * m))
+        em = np.block([[em_upper], [em_lower]])
+
+        ms = linalg.expm(em)
+
+        # Get the three blocks from upper rows
+        ms11 = ms[:n, 0:n]
+        ms12 = ms[:n, n:n + m]
+        ms13 = ms[:n, n + m:]
+
+        ad = ms11
+        bd = ms12 - ms13 + ms11 @ ms13
+        cd = c
+        dd = d + c @ ms13
+
+    elif method == 'impulse':
+        if not np.allclose(d, 0):
+            raise ValueError("Impulse method is only applicable "
+                             "to strictly proper systems")
+
+        ad = linalg.expm(a * dt)
+        bd = ad @ b * dt
+        cd = c
+        dd = c @ b * dt
+
+    else:
+        raise ValueError(f"Unknown transformation method '{method}'")
+
+    return ad, bd, cd, dd, dt

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_max_len_seq.py

@@ -0,0 +1,139 @@
+# Author: Eric Larson
+# 2014
+
+"""Tools for MLS generation"""
+
+import numpy as np
+
+from ._max_len_seq_inner import _max_len_seq_inner
+
+__all__ = ['max_len_seq']
+
+
+# These are definitions of linear shift register taps for use in max_len_seq()
+_mls_taps = {2: [1], 3: [2], 4: [3], 5: [3], 6: [5], 7: [6], 8: [7, 6, 1],
+             9: [5], 10: [7], 11: [9], 12: [11, 10, 4], 13: [12, 11, 8],
+             14: [13, 12, 2], 15: [14], 16: [15, 13, 4], 17: [14],
+             18: [11], 19: [18, 17, 14], 20: [17], 21: [19], 22: [21],
+             23: [18], 24: [23, 22, 17], 25: [22], 26: [25, 24, 20],
+             27: [26, 25, 22], 28: [25], 29: [27], 30: [29, 28, 7],
+             31: [28], 32: [31, 30, 10]}
+
+def max_len_seq(nbits, state=None, length=None, taps=None):
+    """
+    Maximum length sequence (MLS) generator.
+
+    Parameters
+    ----------
+    nbits : int
+        Number of bits to use. Length of the resulting sequence will
+        be ``(2**nbits) - 1``. Note that generating long sequences
+        (e.g., greater than ``nbits == 16``) can take a long time.
+    state : array_like, optional
+        If array, must be of length ``nbits``, and will be cast to binary
+        (bool) representation. If None, a seed of ones will be used,
+        producing a repeatable representation. If ``state`` is all
+        zeros, an error is raised as this is invalid. Default: None.
+    length : int, optional
+        Number of samples to compute. If None, the entire length
+        ``(2**nbits) - 1`` is computed.
+    taps : array_like, optional
+        Polynomial taps to use (e.g., ``[7, 6, 1]`` for an 8-bit sequence).
+        If None, taps will be automatically selected (for up to
+        ``nbits == 32``).
+
+    Returns
+    -------
+    seq : array
+        Resulting MLS sequence of 0's and 1's.
+    state : array
+        The final state of the shift register.
+
+    Notes
+    -----
+    The algorithm for MLS generation is generically described in:
+
+        https://en.wikipedia.org/wiki/Maximum_length_sequence
+
+    The default values for taps are specifically taken from the first
+    option listed for each value of ``nbits`` in:
+
+        https://web.archive.org/web/20181001062252/http://www.newwaveinstruments.com/resources/articles/m_sequence_linear_feedback_shift_register_lfsr.htm
+
+    .. versionadded:: 0.15.0
+
+    Examples
+    --------
+    MLS uses binary convention:
+
+    >>> from scipy.signal import max_len_seq
+    >>> max_len_seq(4)[0]
+    array([1, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 0, 0], dtype=int8)
+
+    MLS has a white spectrum (except for DC):
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from numpy.fft import fft, ifft, fftshift, fftfreq
+    >>> seq = max_len_seq(6)[0]*2-1  # +1 and -1
+    >>> spec = fft(seq)
+    >>> N = len(seq)
+    >>> plt.plot(fftshift(fftfreq(N)), fftshift(np.abs(spec)), '.-')
+    >>> plt.margins(0.1, 0.1)
+    >>> plt.grid(True)
+    >>> plt.show()
+
+    Circular autocorrelation of MLS is an impulse:
+
+    >>> acorrcirc = ifft(spec * np.conj(spec)).real
+    >>> plt.figure()
+    >>> plt.plot(np.arange(-N/2+1, N/2+1), fftshift(acorrcirc), '.-')
+    >>> plt.margins(0.1, 0.1)
+    >>> plt.grid(True)
+    >>> plt.show()
+
+    Linear autocorrelation of MLS is approximately an impulse:
+
+    >>> acorr = np.correlate(seq, seq, 'full')
+    >>> plt.figure()
+    >>> plt.plot(np.arange(-N+1, N), acorr, '.-')
+    >>> plt.margins(0.1, 0.1)
+    >>> plt.grid(True)
+    >>> plt.show()
+
+    """
+    taps_dtype = np.int32 if np.intp().itemsize == 4 else np.int64
+    if taps is None:
+        if nbits not in _mls_taps:
+            known_taps = np.array(list(_mls_taps.keys()))
+            raise ValueError(f'nbits must be between {known_taps.min()} and '
+                             f'{known_taps.max()} if taps is None')
+        taps = np.array(_mls_taps[nbits], taps_dtype)
+    else:
+        taps = np.unique(np.array(taps, taps_dtype))[::-1]
+        if np.any(taps < 0) or np.any(taps > nbits) or taps.size < 1:
+            raise ValueError('taps must be non-empty with values between '
+                             'zero and nbits (inclusive)')
+        taps = np.array(taps)  # needed for Cython and Pythran
+    n_max = (2**nbits) - 1
+    if length is None:
+        length = n_max
+    else:
+        length = int(length)
+        if length < 0:
+            raise ValueError('length must be greater than or equal to 0')
+    # We use int8 instead of bool here because NumPy arrays of bools
+    # don't seem to work nicely with Cython
+    if state is None:
+        state = np.ones(nbits, dtype=np.int8, order='c')
+    else:
+        # makes a copy if need be, ensuring it's 0's and 1's
+        state = np.array(state, dtype=bool, order='c').astype(np.int8)
+    if state.ndim != 1 or state.size != nbits:
+        raise ValueError('state must be a 1-D array of size nbits')
+    if np.all(state == 0):
+        raise ValueError('state must not be all zeros')
+
+    seq = np.empty(length, dtype=np.int8, order='c')
+    state = _max_len_seq_inner(taps, state, nbits, length, seq)
+    return seq, state

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_peak_finding.py

@@ -0,0 +1,1310 @@
+"""
+Functions for identifying peaks in signals.
+"""
+import math
+import numpy as np
+
+from scipy.signal._wavelets import _cwt, _ricker
+from scipy.stats import scoreatpercentile
+
+from ._peak_finding_utils import (
+    _local_maxima_1d,
+    _select_by_peak_distance,
+    _peak_prominences,
+    _peak_widths
+)
+
+
+__all__ = ['argrelmin', 'argrelmax', 'argrelextrema', 'peak_prominences',
+           'peak_widths', 'find_peaks', 'find_peaks_cwt']
+
+
+def _boolrelextrema(data, comparator, axis=0, order=1, mode='clip'):
+    """
+    Calculate the relative extrema of `data`.
+
+    Relative extrema are calculated by finding locations where
+    ``comparator(data[n], data[n+1:n+order+1])`` is True.
+
+    Parameters
+    ----------
+    data : ndarray
+        Array in which to find the relative extrema.
+    comparator : callable
+        Function to use to compare two data points.
+        Should take two arrays as arguments.
+    axis : int, optional
+        Axis over which to select from `data`. Default is 0.
+    order : int, optional
+        How many points on each side to use for the comparison
+        to consider ``comparator(n,n+x)`` to be True.
+    mode : str, optional
+        How the edges of the vector are treated. 'wrap' (wrap around) or
+        'clip' (treat overflow as the same as the last (or first) element).
+        Default 'clip'. See numpy.take.
+
+    Returns
+    -------
+    extrema : ndarray
+        Boolean array of the same shape as `data` that is True at an extrema,
+        False otherwise.
+
+    See also
+    --------
+    argrelmax, argrelmin
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal._peak_finding import _boolrelextrema
+    >>> testdata = np.array([1,2,3,2,1])
+    >>> _boolrelextrema(testdata, np.greater, axis=0)
+    array([False, False,  True, False, False], dtype=bool)
+
+    """
+    if (int(order) != order) or (order < 1):
+        raise ValueError('Order must be an int >= 1')
+
+    datalen = data.shape[axis]
+    locs = np.arange(0, datalen)
+
+    results = np.ones(data.shape, dtype=bool)
+    main = data.take(locs, axis=axis, mode=mode)
+    for shift in range(1, order + 1):
+        plus = data.take(locs + shift, axis=axis, mode=mode)
+        minus = data.take(locs - shift, axis=axis, mode=mode)
+        results &= comparator(main, plus)
+        results &= comparator(main, minus)
+        if ~results.any():
+            return results
+    return results
+
+
+def argrelmin(data, axis=0, order=1, mode='clip'):
+    """
+    Calculate the relative minima of `data`.
+
+    Parameters
+    ----------
+    data : ndarray
+        Array in which to find the relative minima.
+    axis : int, optional
+        Axis over which to select from `data`. Default is 0.
+    order : int, optional
+        How many points on each side to use for the comparison
+        to consider ``comparator(n, n+x)`` to be True.
+    mode : str, optional
+        How the edges of the vector are treated.
+        Available options are 'wrap' (wrap around) or 'clip' (treat overflow
+        as the same as the last (or first) element).
+        Default 'clip'. See numpy.take.
+
+    Returns
+    -------
+    extrema : tuple of ndarrays
+        Indices of the minima in arrays of integers. ``extrema[k]`` is
+        the array of indices of axis `k` of `data`. Note that the
+        return value is a tuple even when `data` is 1-D.
+
+    See Also
+    --------
+    argrelextrema, argrelmax, find_peaks
+
+    Notes
+    -----
+    This function uses `argrelextrema` with np.less as comparator. Therefore, it
+    requires a strict inequality on both sides of a value to consider it a
+    minimum. This means flat minima (more than one sample wide) are not detected.
+    In case of 1-D `data` `find_peaks` can be used to detect all
+    local minima, including flat ones, by calling it with negated `data`.
+
+    .. versionadded:: 0.11.0
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal import argrelmin
+    >>> x = np.array([2, 1, 2, 3, 2, 0, 1, 0])
+    >>> argrelmin(x)
+    (array([1, 5]),)
+    >>> y = np.array([[1, 2, 1, 2],
+    ...               [2, 2, 0, 0],
+    ...               [5, 3, 4, 4]])
+    ...
+    >>> argrelmin(y, axis=1)
+    (array([0, 2]), array([2, 1]))
+
+    """
+    return argrelextrema(data, np.less, axis, order, mode)
+
+
+def argrelmax(data, axis=0, order=1, mode='clip'):
+    """
+    Calculate the relative maxima of `data`.
+
+    Parameters
+    ----------
+    data : ndarray
+        Array in which to find the relative maxima.
+    axis : int, optional
+        Axis over which to select from `data`. Default is 0.
+    order : int, optional
+        How many points on each side to use for the comparison
+        to consider ``comparator(n, n+x)`` to be True.
+    mode : str, optional
+        How the edges of the vector are treated.
+        Available options are 'wrap' (wrap around) or 'clip' (treat overflow
+        as the same as the last (or first) element).
+        Default 'clip'. See `numpy.take`.
+
+    Returns
+    -------
+    extrema : tuple of ndarrays
+        Indices of the maxima in arrays of integers. ``extrema[k]`` is
+        the array of indices of axis `k` of `data`. Note that the
+        return value is a tuple even when `data` is 1-D.
+
+    See Also
+    --------
+    argrelextrema, argrelmin, find_peaks
+
+    Notes
+    -----
+    This function uses `argrelextrema` with np.greater as comparator. Therefore,
+    it  requires a strict inequality on both sides of a value to consider it a
+    maximum. This means flat maxima (more than one sample wide) are not detected.
+    In case of 1-D `data` `find_peaks` can be used to detect all
+    local maxima, including flat ones.
+
+    .. versionadded:: 0.11.0
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal import argrelmax
+    >>> x = np.array([2, 1, 2, 3, 2, 0, 1, 0])
+    >>> argrelmax(x)
+    (array([3, 6]),)
+    >>> y = np.array([[1, 2, 1, 2],
+    ...               [2, 2, 0, 0],
+    ...               [5, 3, 4, 4]])
+    ...
+    >>> argrelmax(y, axis=1)
+    (array([0]), array([1]))
+    """
+    return argrelextrema(data, np.greater, axis, order, mode)
+
+
+def argrelextrema(data, comparator, axis=0, order=1, mode='clip'):
+    """
+    Calculate the relative extrema of `data`.
+
+    Parameters
+    ----------
+    data : ndarray
+        Array in which to find the relative extrema.
+    comparator : callable
+        Function to use to compare two data points.
+        Should take two arrays as arguments.
+    axis : int, optional
+        Axis over which to select from `data`. Default is 0.
+    order : int, optional
+        How many points on each side to use for the comparison
+        to consider ``comparator(n, n+x)`` to be True.
+    mode : str, optional
+        How the edges of the vector are treated. 'wrap' (wrap around) or
+        'clip' (treat overflow as the same as the last (or first) element).
+        Default is 'clip'. See `numpy.take`.
+
+    Returns
+    -------
+    extrema : tuple of ndarrays
+        Indices of the maxima in arrays of integers. ``extrema[k]`` is
+        the array of indices of axis `k` of `data`. Note that the
+        return value is a tuple even when `data` is 1-D.
+
+    See Also
+    --------
+    argrelmin, argrelmax
+
+    Notes
+    -----
+
+    .. versionadded:: 0.11.0
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal import argrelextrema
+    >>> x = np.array([2, 1, 2, 3, 2, 0, 1, 0])
+    >>> argrelextrema(x, np.greater)
+    (array([3, 6]),)
+    >>> y = np.array([[1, 2, 1, 2],
+    ...               [2, 2, 0, 0],
+    ...               [5, 3, 4, 4]])
+    ...
+    >>> argrelextrema(y, np.less, axis=1)
+    (array([0, 2]), array([2, 1]))
+
+    """
+    results = _boolrelextrema(data, comparator,
+                              axis, order, mode)
+    return np.nonzero(results)
+
+
+def _arg_x_as_expected(value):
+    """Ensure argument `x` is a 1-D C-contiguous array of dtype('float64').
+
+    Used in `find_peaks`, `peak_prominences` and `peak_widths` to make `x`
+    compatible with the signature of the wrapped Cython functions.
+
+    Returns
+    -------
+    value : ndarray
+        A 1-D C-contiguous array with dtype('float64').
+    """
+    value = np.asarray(value, order='C', dtype=np.float64)
+    if value.ndim != 1:
+        raise ValueError('`x` must be a 1-D array')
+    return value
+
+
+def _arg_peaks_as_expected(value):
+    """Ensure argument `peaks` is a 1-D C-contiguous array of dtype('intp').
+
+    Used in `peak_prominences` and `peak_widths` to make `peaks` compatible
+    with the signature of the wrapped Cython functions.
+
+    Returns
+    -------
+    value : ndarray
+        A 1-D C-contiguous array with dtype('intp').
+    """
+    value = np.asarray(value)
+    if value.size == 0:
+        # Empty arrays default to np.float64 but are valid input
+        value = np.array([], dtype=np.intp)
+    try:
+        # Safely convert to C-contiguous array of type np.intp
+        value = value.astype(np.intp, order='C', casting='safe',
+                             subok=False, copy=False)
+    except TypeError as e:
+        raise TypeError("cannot safely cast `peaks` to dtype('intp')") from e
+    if value.ndim != 1:
+        raise ValueError('`peaks` must be a 1-D array')
+    return value
+
+
+def _arg_wlen_as_expected(value):
+    """Ensure argument `wlen` is of type `np.intp` and larger than 1.
+
+    Used in `peak_prominences` and `peak_widths`.
+
+    Returns
+    -------
+    value : np.intp
+        The original `value` rounded up to an integer or -1 if `value` was
+        None.
+    """
+    if value is None:
+        # _peak_prominences expects an intp; -1 signals that no value was
+        # supplied by the user
+        value = -1
+    elif 1 < value:
+        # Round up to a positive integer
+        if isinstance(value, float):
+            value = math.ceil(value)
+        value = np.intp(value)
+    else:
+        raise ValueError(f'`wlen` must be larger than 1, was {value}')
+    return value
+
+
+def peak_prominences(x, peaks, wlen=None):
+    """
+    Calculate the prominence of each peak in a signal.
+
+    The prominence of a peak measures how much a peak stands out from the
+    surrounding baseline of the signal and is defined as the vertical distance
+    between the peak and its lowest contour line.
+
+    Parameters
+    ----------
+    x : sequence
+        A signal with peaks.
+    peaks : sequence
+        Indices of peaks in `x`.
+    wlen : int, optional
+        A window length in samples that optionally limits the evaluated area for
+        each peak to a subset of `x`. The peak is always placed in the middle of
+        the window therefore the given length is rounded up to the next odd
+        integer. This parameter can speed up the calculation (see Notes).
+
+    Returns
+    -------
+    prominences : ndarray
+        The calculated prominences for each peak in `peaks`.
+    left_bases, right_bases : ndarray
+        The peaks' bases as indices in `x` to the left and right of each peak.
+        The higher base of each pair is a peak's lowest contour line.
+
+    Raises
+    ------
+    ValueError
+        If a value in `peaks` is an invalid index for `x`.
+
+    Warns
+    -----
+    PeakPropertyWarning
+        For indices in `peaks` that don't point to valid local maxima in `x`,
+        the returned prominence will be 0 and this warning is raised. This
+        also happens if `wlen` is smaller than the plateau size of a peak.
+
+    Warnings
+    --------
+    This function may return unexpected results for data containing NaNs. To
+    avoid this, NaNs should either be removed or replaced.
+
+    See Also
+    --------
+    find_peaks
+        Find peaks inside a signal based on peak properties.
+    peak_widths
+        Calculate the width of peaks.
+
+    Notes
+    -----
+    Strategy to compute a peak's prominence:
+
+    1. Extend a horizontal line from the current peak to the left and right
+       until the line either reaches the window border (see `wlen`) or
+       intersects the signal again at the slope of a higher peak. An
+       intersection with a peak of the same height is ignored.
+    2. On each side find the minimal signal value within the interval defined
+       above. These points are the peak's bases.
+    3. The higher one of the two bases marks the peak's lowest contour line. The
+       prominence can then be calculated as the vertical difference between the
+       peaks height itself and its lowest contour line.
+
+    Searching for the peak's bases can be slow for large `x` with periodic
+    behavior because large chunks or even the full signal need to be evaluated
+    for the first algorithmic step. This evaluation area can be limited with the
+    parameter `wlen` which restricts the algorithm to a window around the
+    current peak and can shorten the calculation time if the window length is
+    short in relation to `x`.
+    However, this may stop the algorithm from finding the true global contour
+    line if the peak's true bases are outside this window. Instead, a higher
+    contour line is found within the restricted window leading to a smaller
+    calculated prominence. In practice, this is only relevant for the highest set
+    of peaks in `x`. This behavior may even be used intentionally to calculate
+    "local" prominences.
+
+    .. versionadded:: 1.1.0
+
+    References
+    ----------
+    .. [1] Wikipedia Article for Topographic Prominence:
+       https://en.wikipedia.org/wiki/Topographic_prominence
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal import find_peaks, peak_prominences
+    >>> import matplotlib.pyplot as plt
+
+    Create a test signal with two overlaid harmonics
+
+    >>> x = np.linspace(0, 6 * np.pi, 1000)
+    >>> x = np.sin(x) + 0.6 * np.sin(2.6 * x)
+
+    Find all peaks and calculate prominences
+
+    >>> peaks, _ = find_peaks(x)
+    >>> prominences = peak_prominences(x, peaks)[0]
+    >>> prominences
+    array([1.24159486, 0.47840168, 0.28470524, 3.10716793, 0.284603  ,
+           0.47822491, 2.48340261, 0.47822491])
+
+    Calculate the height of each peak's contour line and plot the results
+
+    >>> contour_heights = x[peaks] - prominences
+    >>> plt.plot(x)
+    >>> plt.plot(peaks, x[peaks], "x")
+    >>> plt.vlines(x=peaks, ymin=contour_heights, ymax=x[peaks])
+    >>> plt.show()
+
+    Let's evaluate a second example that demonstrates several edge cases for
+    one peak at index 5.
+
+    >>> x = np.array([0, 1, 0, 3, 1, 3, 0, 4, 0])
+    >>> peaks = np.array([5])
+    >>> plt.plot(x)
+    >>> plt.plot(peaks, x[peaks], "x")
+    >>> plt.show()
+    >>> peak_prominences(x, peaks)  # -> (prominences, left_bases, right_bases)
+    (array([3.]), array([2]), array([6]))
+
+    Note how the peak at index 3 of the same height is not considered as a
+    border while searching for the left base. Instead, two minima at 0 and 2
+    are found in which case the one closer to the evaluated peak is always
+    chosen. On the right side, however, the base must be placed at 6 because the
+    higher peak represents the right border to the evaluated area.
+
+    >>> peak_prominences(x, peaks, wlen=3.1)
+    (array([2.]), array([4]), array([6]))
+
+    Here, we restricted the algorithm to a window from 3 to 7 (the length is 5
+    samples because `wlen` was rounded up to the next odd integer). Thus, the
+    only two candidates in the evaluated area are the two neighboring samples
+    and a smaller prominence is calculated.
+    """
+    x = _arg_x_as_expected(x)
+    peaks = _arg_peaks_as_expected(peaks)
+    wlen = _arg_wlen_as_expected(wlen)
+    return _peak_prominences(x, peaks, wlen)
+
+
+def peak_widths(x, peaks, rel_height=0.5, prominence_data=None, wlen=None):
+    """
+    Calculate the width of each peak in a signal.
+
+    This function calculates the width of a peak in samples at a relative
+    distance to the peak's height and prominence.
+
+    Parameters
+    ----------
+    x : sequence
+        A signal with peaks.
+    peaks : sequence
+        Indices of peaks in `x`.
+    rel_height : float, optional
+        Chooses the relative height at which the peak width is measured as a
+        percentage of its prominence. 1.0 calculates the width of the peak at
+        its lowest contour line while 0.5 evaluates at half the prominence
+        height. Must be at least 0. See notes for further explanation.
+    prominence_data : tuple, optional
+        A tuple of three arrays matching the output of `peak_prominences` when
+        called with the same arguments `x` and `peaks`. This data are calculated
+        internally if not provided.
+    wlen : int, optional
+        A window length in samples passed to `peak_prominences` as an optional
+        argument for internal calculation of `prominence_data`. This argument
+        is ignored if `prominence_data` is given.
+
+    Returns
+    -------
+    widths : ndarray
+        The widths for each peak in samples.
+    width_heights : ndarray
+        The height of the contour lines at which the `widths` where evaluated.
+    left_ips, right_ips : ndarray
+        Interpolated positions of left and right intersection points of a
+        horizontal line at the respective evaluation height.
+
+    Raises
+    ------
+    ValueError
+        If `prominence_data` is supplied but doesn't satisfy the condition
+        ``0 <= left_base <= peak <= right_base < x.shape[0]`` for each peak,
+        has the wrong dtype, is not C-contiguous or does not have the same
+        shape.
+
+    Warns
+    -----
+    PeakPropertyWarning
+        Raised if any calculated width is 0. This may stem from the supplied
+        `prominence_data` or if `rel_height` is set to 0.
+
+    Warnings
+    --------
+    This function may return unexpected results for data containing NaNs. To
+    avoid this, NaNs should either be removed or replaced.
+
+    See Also
+    --------
+    find_peaks
+        Find peaks inside a signal based on peak properties.
+    peak_prominences
+        Calculate the prominence of peaks.
+
+    Notes
+    -----
+    The basic algorithm to calculate a peak's width is as follows:
+
+    * Calculate the evaluation height :math:`h_{eval}` with the formula
+      :math:`h_{eval} = h_{Peak} - P \\cdot R`, where :math:`h_{Peak}` is the
+      height of the peak itself, :math:`P` is the peak's prominence and
+      :math:`R` a positive ratio specified with the argument `rel_height`.
+    * Draw a horizontal line at the evaluation height to both sides, starting at
+      the peak's current vertical position until the lines either intersect a
+      slope, the signal border or cross the vertical position of the peak's
+      base (see `peak_prominences` for an definition). For the first case,
+      intersection with the signal, the true intersection point is estimated
+      with linear interpolation.
+    * Calculate the width as the horizontal distance between the chosen
+      endpoints on both sides. As a consequence of this the maximal possible
+      width for each peak is the horizontal distance between its bases.
+
+    As shown above to calculate a peak's width its prominence and bases must be
+    known. You can supply these yourself with the argument `prominence_data`.
+    Otherwise, they are internally calculated (see `peak_prominences`).
+
+    .. versionadded:: 1.1.0
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal import chirp, find_peaks, peak_widths
+    >>> import matplotlib.pyplot as plt
+
+    Create a test signal with two overlaid harmonics
+
+    >>> x = np.linspace(0, 6 * np.pi, 1000)
+    >>> x = np.sin(x) + 0.6 * np.sin(2.6 * x)
+
+    Find all peaks and calculate their widths at the relative height of 0.5
+    (contour line at half the prominence height) and 1 (at the lowest contour
+    line at full prominence height).
+
+    >>> peaks, _ = find_peaks(x)
+    >>> results_half = peak_widths(x, peaks, rel_height=0.5)
+    >>> results_half[0]  # widths
+    array([ 64.25172825,  41.29465463,  35.46943289, 104.71586081,
+            35.46729324,  41.30429622, 181.93835853,  45.37078546])
+    >>> results_full = peak_widths(x, peaks, rel_height=1)
+    >>> results_full[0]  # widths
+    array([181.9396084 ,  72.99284945,  61.28657872, 373.84622694,
+        61.78404617,  72.48822812, 253.09161876,  79.36860878])
+
+    Plot signal, peaks and contour lines at which the widths where calculated
+
+    >>> plt.plot(x)
+    >>> plt.plot(peaks, x[peaks], "x")
+    >>> plt.hlines(*results_half[1:], color="C2")
+    >>> plt.hlines(*results_full[1:], color="C3")
+    >>> plt.show()
+    """
+    x = _arg_x_as_expected(x)
+    peaks = _arg_peaks_as_expected(peaks)
+    if prominence_data is None:
+        # Calculate prominence if not supplied and use wlen if supplied.
+        wlen = _arg_wlen_as_expected(wlen)
+        prominence_data = _peak_prominences(x, peaks, wlen)
+    return _peak_widths(x, peaks, rel_height, *prominence_data)
+
+
+def _unpack_condition_args(interval, x, peaks):
+    """
+    Parse condition arguments for `find_peaks`.
+
+    Parameters
+    ----------
+    interval : number or ndarray or sequence
+        Either a number or ndarray or a 2-element sequence of the former. The
+        first value is always interpreted as `imin` and the second, if supplied,
+        as `imax`.
+    x : ndarray
+        The signal with `peaks`.
+    peaks : ndarray
+        An array with indices used to reduce `imin` and / or `imax` if those are
+        arrays.
+
+    Returns
+    -------
+    imin, imax : number or ndarray or None
+        Minimal and maximal value in `argument`.
+
+    Raises
+    ------
+    ValueError :
+        If interval border is given as array and its size does not match the size
+        of `x`.
+
+    Notes
+    -----
+
+    .. versionadded:: 1.1.0
+    """
+    try:
+        imin, imax = interval
+    except (TypeError, ValueError):
+        imin, imax = (interval, None)
+
+    # Reduce arrays if arrays
+    if isinstance(imin, np.ndarray):
+        if imin.size != x.size:
+            raise ValueError('array size of lower interval border must match x')
+        imin = imin[peaks]
+    if isinstance(imax, np.ndarray):
+        if imax.size != x.size:
+            raise ValueError('array size of upper interval border must match x')
+        imax = imax[peaks]
+
+    return imin, imax
+
+
+def _select_by_property(peak_properties, pmin, pmax):
+    """
+    Evaluate where the generic property of peaks confirms to an interval.
+
+    Parameters
+    ----------
+    peak_properties : ndarray
+        An array with properties for each peak.
+    pmin : None or number or ndarray
+        Lower interval boundary for `peak_properties`. ``None`` is interpreted as
+        an open border.
+    pmax : None or number or ndarray
+        Upper interval boundary for `peak_properties`. ``None`` is interpreted as
+        an open border.
+
+    Returns
+    -------
+    keep : bool
+        A boolean mask evaluating to true where `peak_properties` confirms to the
+        interval.
+
+    See Also
+    --------
+    find_peaks
+
+    Notes
+    -----
+
+    .. versionadded:: 1.1.0
+    """
+    keep = np.ones(peak_properties.size, dtype=bool)
+    if pmin is not None:
+        keep &= (pmin <= peak_properties)
+    if pmax is not None:
+        keep &= (peak_properties <= pmax)
+    return keep
+
+
+def _select_by_peak_threshold(x, peaks, tmin, tmax):
+    """
+    Evaluate which peaks fulfill the threshold condition.
+
+    Parameters
+    ----------
+    x : ndarray
+        A 1-D array which is indexable by `peaks`.
+    peaks : ndarray
+        Indices of peaks in `x`.
+    tmin, tmax : scalar or ndarray or None
+         Minimal and / or maximal required thresholds. If supplied as ndarrays
+         their size must match `peaks`. ``None`` is interpreted as an open
+         border.
+
+    Returns
+    -------
+    keep : bool
+        A boolean mask evaluating to true where `peaks` fulfill the threshold
+        condition.
+    left_thresholds, right_thresholds : ndarray
+        Array matching `peak` containing the thresholds of each peak on
+        both sides.
+
+    Notes
+    -----
+
+    .. versionadded:: 1.1.0
+    """
+    # Stack thresholds on both sides to make min / max operations easier:
+    # tmin is compared with the smaller, and tmax with the greater threshold to
+    # each peak's side
+    stacked_thresholds = np.vstack([x[peaks] - x[peaks - 1],
+                                    x[peaks] - x[peaks + 1]])
+    keep = np.ones(peaks.size, dtype=bool)
+    if tmin is not None:
+        min_thresholds = np.min(stacked_thresholds, axis=0)
+        keep &= (tmin <= min_thresholds)
+    if tmax is not None:
+        max_thresholds = np.max(stacked_thresholds, axis=0)
+        keep &= (max_thresholds <= tmax)
+
+    return keep, stacked_thresholds[0], stacked_thresholds[1]
+
+
+def find_peaks(x, height=None, threshold=None, distance=None,
+               prominence=None, width=None, wlen=None, rel_height=0.5,
+               plateau_size=None):
+    """
+    Find peaks inside a signal based on peak properties.
+
+    This function takes a 1-D array and finds all local maxima by
+    simple comparison of neighboring values. Optionally, a subset of these
+    peaks can be selected by specifying conditions for a peak's properties.
+
+    Parameters
+    ----------
+    x : sequence
+        A signal with peaks.
+    height : number or ndarray or sequence, optional
+        Required height of peaks. Either a number, ``None``, an array matching
+        `x` or a 2-element sequence of the former. The first element is
+        always interpreted as the  minimal and the second, if supplied, as the
+        maximal required height.
+    threshold : number or ndarray or sequence, optional
+        Required threshold of peaks, the vertical distance to its neighboring
+        samples. Either a number, ``None``, an array matching `x` or a
+        2-element sequence of the former. The first element is always
+        interpreted as the  minimal and the second, if supplied, as the maximal
+        required threshold.
+    distance : number, optional
+        Required minimal horizontal distance (>= 1) in samples between
+        neighbouring peaks. Smaller peaks are removed first until the condition
+        is fulfilled for all remaining peaks.
+    prominence : number or ndarray or sequence, optional
+        Required prominence of peaks. Either a number, ``None``, an array
+        matching `x` or a 2-element sequence of the former. The first
+        element is always interpreted as the  minimal and the second, if
+        supplied, as the maximal required prominence.
+    width : number or ndarray or sequence, optional
+        Required width of peaks in samples. Either a number, ``None``, an array
+        matching `x` or a 2-element sequence of the former. The first
+        element is always interpreted as the  minimal and the second, if
+        supplied, as the maximal required width.
+    wlen : int, optional
+        Used for calculation of the peaks prominences, thus it is only used if
+        one of the arguments `prominence` or `width` is given. See argument
+        `wlen` in `peak_prominences` for a full description of its effects.
+    rel_height : float, optional
+        Used for calculation of the peaks width, thus it is only used if `width`
+        is given. See argument  `rel_height` in `peak_widths` for a full
+        description of its effects.
+    plateau_size : number or ndarray or sequence, optional
+        Required size of the flat top of peaks in samples. Either a number,
+        ``None``, an array matching `x` or a 2-element sequence of the former.
+        The first element is always interpreted as the minimal and the second,
+        if supplied as the maximal required plateau size.
+
+        .. versionadded:: 1.2.0
+
+    Returns
+    -------
+    peaks : ndarray
+        Indices of peaks in `x` that satisfy all given conditions.
+    properties : dict
+        A dictionary containing properties of the returned peaks which were
+        calculated as intermediate results during evaluation of the specified
+        conditions:
+
+        * 'peak_heights'
+              If `height` is given, the height of each peak in `x`.
+        * 'left_thresholds', 'right_thresholds'
+              If `threshold` is given, these keys contain a peaks vertical
+              distance to its neighbouring samples.
+        * 'prominences', 'right_bases', 'left_bases'
+              If `prominence` is given, these keys are accessible. See
+              `peak_prominences` for a description of their content.
+        * 'widths', 'width_heights', 'left_ips', 'right_ips'
+              If `width` is given, these keys are accessible. See `peak_widths`
+              for a description of their content.
+        * 'plateau_sizes', left_edges', 'right_edges'
+              If `plateau_size` is given, these keys are accessible and contain
+              the indices of a peak's edges (edges are still part of the
+              plateau) and the calculated plateau sizes.
+
+              .. versionadded:: 1.2.0
+
+        To calculate and return properties without excluding peaks, provide the
+        open interval ``(None, None)`` as a value to the appropriate argument
+        (excluding `distance`).
+
+    Warns
+    -----
+    PeakPropertyWarning
+        Raised if a peak's properties have unexpected values (see
+        `peak_prominences` and `peak_widths`).
+
+    Warnings
+    --------
+    This function may return unexpected results for data containing NaNs. To
+    avoid this, NaNs should either be removed or replaced.
+
+    See Also
+    --------
+    find_peaks_cwt
+        Find peaks using the wavelet transformation.
+    peak_prominences
+        Directly calculate the prominence of peaks.
+    peak_widths
+        Directly calculate the width of peaks.
+
+    Notes
+    -----
+    In the context of this function, a peak or local maximum is defined as any
+    sample whose two direct neighbours have a smaller amplitude. For flat peaks
+    (more than one sample of equal amplitude wide) the index of the middle
+    sample is returned (rounded down in case the number of samples is even).
+    For noisy signals the peak locations can be off because the noise might
+    change the position of local maxima. In those cases consider smoothing the
+    signal before searching for peaks or use other peak finding and fitting
+    methods (like `find_peaks_cwt`).
+
+    Some additional comments on specifying conditions:
+
+    * Almost all conditions (excluding `distance`) can be given as half-open or
+      closed intervals, e.g., ``1`` or ``(1, None)`` defines the half-open
+      interval :math:`[1, \\infty]` while ``(None, 1)`` defines the interval
+      :math:`[-\\infty, 1]`. The open interval ``(None, None)`` can be specified
+      as well, which returns the matching properties without exclusion of peaks.
+    * The border is always included in the interval used to select valid peaks.
+    * For several conditions the interval borders can be specified with
+      arrays matching `x` in shape which enables dynamic constrains based on
+      the sample position.
+    * The conditions are evaluated in the following order: `plateau_size`,
+      `height`, `threshold`, `distance`, `prominence`, `width`. In most cases
+      this order is the fastest one because faster operations are applied first
+      to reduce the number of peaks that need to be evaluated later.
+    * While indices in `peaks` are guaranteed to be at least `distance` samples
+      apart, edges of flat peaks may be closer than the allowed `distance`.
+    * Use `wlen` to reduce the time it takes to evaluate the conditions for
+      `prominence` or `width` if `x` is large or has many local maxima
+      (see `peak_prominences`).
+
+    .. versionadded:: 1.1.0
+
+    Examples
+    --------
+    To demonstrate this function's usage we use a signal `x` supplied with
+    SciPy (see `scipy.datasets.electrocardiogram`). Let's find all peaks (local
+    maxima) in `x` whose amplitude lies above 0.
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.datasets import electrocardiogram
+    >>> from scipy.signal import find_peaks
+    >>> x = electrocardiogram()[2000:4000]
+    >>> peaks, _ = find_peaks(x, height=0)
+    >>> plt.plot(x)
+    >>> plt.plot(peaks, x[peaks], "x")
+    >>> plt.plot(np.zeros_like(x), "--", color="gray")
+    >>> plt.show()
+
+    We can select peaks below 0 with ``height=(None, 0)`` or use arrays matching
+    `x` in size to reflect a changing condition for different parts of the
+    signal.
+
+    >>> border = np.sin(np.linspace(0, 3 * np.pi, x.size))
+    >>> peaks, _ = find_peaks(x, height=(-border, border))
+    >>> plt.plot(x)
+    >>> plt.plot(-border, "--", color="gray")
+    >>> plt.plot(border, ":", color="gray")
+    >>> plt.plot(peaks, x[peaks], "x")
+    >>> plt.show()
+
+    Another useful condition for periodic signals can be given with the
+    `distance` argument. In this case, we can easily select the positions of
+    QRS complexes within the electrocardiogram (ECG) by demanding a distance of
+    at least 150 samples.
+
+    >>> peaks, _ = find_peaks(x, distance=150)
+    >>> np.diff(peaks)
+    array([186, 180, 177, 171, 177, 169, 167, 164, 158, 162, 172])
+    >>> plt.plot(x)
+    >>> plt.plot(peaks, x[peaks], "x")
+    >>> plt.show()
+
+    Especially for noisy signals peaks can be easily grouped by their
+    prominence (see `peak_prominences`). E.g., we can select all peaks except
+    for the mentioned QRS complexes by limiting the allowed prominence to 0.6.
+
+    >>> peaks, properties = find_peaks(x, prominence=(None, 0.6))
+    >>> properties["prominences"].max()
+    0.5049999999999999
+    >>> plt.plot(x)
+    >>> plt.plot(peaks, x[peaks], "x")
+    >>> plt.show()
+
+    And, finally, let's examine a different section of the ECG which contains
+    beat forms of different shape. To select only the atypical heart beats, we
+    combine two conditions: a minimal prominence of 1 and width of at least 20
+    samples.
+
+    >>> x = electrocardiogram()[17000:18000]
+    >>> peaks, properties = find_peaks(x, prominence=1, width=20)
+    >>> properties["prominences"], properties["widths"]
+    (array([1.495, 2.3  ]), array([36.93773946, 39.32723577]))
+    >>> plt.plot(x)
+    >>> plt.plot(peaks, x[peaks], "x")
+    >>> plt.vlines(x=peaks, ymin=x[peaks] - properties["prominences"],
+    ...            ymax = x[peaks], color = "C1")
+    >>> plt.hlines(y=properties["width_heights"], xmin=properties["left_ips"],
+    ...            xmax=properties["right_ips"], color = "C1")
+    >>> plt.show()
+    """
+    # _argmaxima1d expects array of dtype 'float64'
+    x = _arg_x_as_expected(x)
+    if distance is not None and distance < 1:
+        raise ValueError('`distance` must be greater or equal to 1')
+
+    peaks, left_edges, right_edges = _local_maxima_1d(x)
+    properties = {}
+
+    if plateau_size is not None:
+        # Evaluate plateau size
+        plateau_sizes = right_edges - left_edges + 1
+        pmin, pmax = _unpack_condition_args(plateau_size, x, peaks)
+        keep = _select_by_property(plateau_sizes, pmin, pmax)
+        peaks = peaks[keep]
+        properties["plateau_sizes"] = plateau_sizes
+        properties["left_edges"] = left_edges
+        properties["right_edges"] = right_edges
+        properties = {key: array[keep] for key, array in properties.items()}
+
+    if height is not None:
+        # Evaluate height condition
+        peak_heights = x[peaks]
+        hmin, hmax = _unpack_condition_args(height, x, peaks)
+        keep = _select_by_property(peak_heights, hmin, hmax)
+        peaks = peaks[keep]
+        properties["peak_heights"] = peak_heights
+        properties = {key: array[keep] for key, array in properties.items()}
+
+    if threshold is not None:
+        # Evaluate threshold condition
+        tmin, tmax = _unpack_condition_args(threshold, x, peaks)
+        keep, left_thresholds, right_thresholds = _select_by_peak_threshold(
+            x, peaks, tmin, tmax)
+        peaks = peaks[keep]
+        properties["left_thresholds"] = left_thresholds
+        properties["right_thresholds"] = right_thresholds
+        properties = {key: array[keep] for key, array in properties.items()}
+
+    if distance is not None:
+        # Evaluate distance condition
+        keep = _select_by_peak_distance(peaks, x[peaks], distance)
+        peaks = peaks[keep]
+        properties = {key: array[keep] for key, array in properties.items()}
+
+    if prominence is not None or width is not None:
+        # Calculate prominence (required for both conditions)
+        wlen = _arg_wlen_as_expected(wlen)
+        properties.update(zip(
+            ['prominences', 'left_bases', 'right_bases'],
+            _peak_prominences(x, peaks, wlen=wlen)
+        ))
+
+    if prominence is not None:
+        # Evaluate prominence condition
+        pmin, pmax = _unpack_condition_args(prominence, x, peaks)
+        keep = _select_by_property(properties['prominences'], pmin, pmax)
+        peaks = peaks[keep]
+        properties = {key: array[keep] for key, array in properties.items()}
+
+    if width is not None:
+        # Calculate widths
+        properties.update(zip(
+            ['widths', 'width_heights', 'left_ips', 'right_ips'],
+            _peak_widths(x, peaks, rel_height, properties['prominences'],
+                         properties['left_bases'], properties['right_bases'])
+        ))
+        # Evaluate width condition
+        wmin, wmax = _unpack_condition_args(width, x, peaks)
+        keep = _select_by_property(properties['widths'], wmin, wmax)
+        peaks = peaks[keep]
+        properties = {key: array[keep] for key, array in properties.items()}
+
+    return peaks, properties
+
+
+def _identify_ridge_lines(matr, max_distances, gap_thresh):
+    """
+    Identify ridges in the 2-D matrix.
+
+    Expect that the width of the wavelet feature increases with increasing row
+    number.
+
+    Parameters
+    ----------
+    matr : 2-D ndarray
+        Matrix in which to identify ridge lines.
+    max_distances : 1-D sequence
+        At each row, a ridge line is only connected
+        if the relative max at row[n] is within
+        `max_distances`[n] from the relative max at row[n+1].
+    gap_thresh : int
+        If a relative maximum is not found within `max_distances`,
+        there will be a gap. A ridge line is discontinued if
+        there are more than `gap_thresh` points without connecting
+        a new relative maximum.
+
+    Returns
+    -------
+    ridge_lines : tuple
+        Tuple of 2 1-D sequences. `ridge_lines`[ii][0] are the rows of the
+        ii-th ridge-line, `ridge_lines`[ii][1] are the columns. Empty if none
+        found.  Each ridge-line will be sorted by row (increasing), but the
+        order of the ridge lines is not specified.
+
+    References
+    ----------
+    .. [1] Bioinformatics (2006) 22 (17): 2059-2065.
+       :doi:`10.1093/bioinformatics/btl355`
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal._peak_finding import _identify_ridge_lines
+    >>> rng = np.random.default_rng()
+    >>> data = rng.random((5,5))
+    >>> max_dist = 3
+    >>> max_distances = np.full(20, max_dist)
+    >>> ridge_lines = _identify_ridge_lines(data, max_distances, 1)
+
+    Notes
+    -----
+    This function is intended to be used in conjunction with `cwt`
+    as part of `find_peaks_cwt`.
+
+    """
+    if len(max_distances) < matr.shape[0]:
+        raise ValueError('Max_distances must have at least as many rows '
+                         'as matr')
+
+    all_max_cols = _boolrelextrema(matr, np.greater, axis=1, order=1)
+    # Highest row for which there are any relative maxima
+    has_relmax = np.nonzero(all_max_cols.any(axis=1))[0]
+    if len(has_relmax) == 0:
+        return []
+    start_row = has_relmax[-1]
+    # Each ridge line is a 3-tuple:
+    # rows, cols,Gap number
+    ridge_lines = [[[start_row],
+                   [col],
+                   0] for col in np.nonzero(all_max_cols[start_row])[0]]
+    final_lines = []
+    rows = np.arange(start_row - 1, -1, -1)
+    cols = np.arange(0, matr.shape[1])
+    for row in rows:
+        this_max_cols = cols[all_max_cols[row]]
+
+        # Increment gap number of each line,
+        # set it to zero later if appropriate
+        for line in ridge_lines:
+            line[2] += 1
+
+        # XXX These should always be all_max_cols[row]
+        # But the order might be different. Might be an efficiency gain
+        # to make sure the order is the same and avoid this iteration
+        prev_ridge_cols = np.array([line[1][-1] for line in ridge_lines])
+        # Look through every relative maximum found at current row
+        # Attempt to connect them with existing ridge lines.
+        for ind, col in enumerate(this_max_cols):
+            # If there is a previous ridge line within
+            # the max_distance to connect to, do so.
+            # Otherwise start a new one.
+            line = None
+            if len(prev_ridge_cols) > 0:
+                diffs = np.abs(col - prev_ridge_cols)
+                closest = np.argmin(diffs)
+                if diffs[closest] <= max_distances[row]:
+                    line = ridge_lines[closest]
+            if line is not None:
+                # Found a point close enough, extend current ridge line
+                line[1].append(col)
+                line[0].append(row)
+                line[2] = 0
+            else:
+                new_line = [[row],
+                            [col],
+                            0]
+                ridge_lines.append(new_line)
+
+        # Remove the ridge lines with gap_number too high
+        # XXX Modifying a list while iterating over it.
+        # Should be safe, since we iterate backwards, but
+        # still tacky.
+        for ind in range(len(ridge_lines) - 1, -1, -1):
+            line = ridge_lines[ind]
+            if line[2] > gap_thresh:
+                final_lines.append(line)
+                del ridge_lines[ind]
+
+    out_lines = []
+    for line in (final_lines + ridge_lines):
+        sortargs = np.array(np.argsort(line[0]))
+        rows, cols = np.zeros_like(sortargs), np.zeros_like(sortargs)
+        rows[sortargs] = line[0]
+        cols[sortargs] = line[1]
+        out_lines.append([rows, cols])
+
+    return out_lines
+
+
+def _filter_ridge_lines(cwt, ridge_lines, window_size=None, min_length=None,
+                        min_snr=1, noise_perc=10):
+    """
+    Filter ridge lines according to prescribed criteria. Intended
+    to be used for finding relative maxima.
+
+    Parameters
+    ----------
+    cwt : 2-D ndarray
+        Continuous wavelet transform from which the `ridge_lines` were defined.
+    ridge_lines : 1-D sequence
+        Each element should contain 2 sequences, the rows and columns
+        of the ridge line (respectively).
+    window_size : int, optional
+        Size of window to use to calculate noise floor.
+        Default is ``cwt.shape[1] / 20``.
+    min_length : int, optional
+        Minimum length a ridge line needs to be acceptable.
+        Default is ``cwt.shape[0] / 4``, ie 1/4-th the number of widths.
+    min_snr : float, optional
+        Minimum SNR ratio. Default 1. The signal is the value of
+        the cwt matrix at the shortest length scale (``cwt[0, loc]``), the
+        noise is the `noise_perc`\\ th percentile of datapoints contained within a
+        window of `window_size` around ``cwt[0, loc]``.
+    noise_perc : float, optional
+        When calculating the noise floor, percentile of data points
+        examined below which to consider noise. Calculated using
+        scipy.stats.scoreatpercentile.
+
+    References
+    ----------
+    .. [1] Bioinformatics (2006) 22 (17): 2059-2065.
+       :doi:`10.1093/bioinformatics/btl355`
+
+    """
+    num_points = cwt.shape[1]
+    if min_length is None:
+        min_length = np.ceil(cwt.shape[0] / 4)
+    if window_size is None:
+        window_size = np.ceil(num_points / 20)
+
+    window_size = int(window_size)
+    hf_window, odd = divmod(window_size, 2)
+
+    # Filter based on SNR
+    row_one = cwt[0, :]
+    noises = np.empty_like(row_one)
+    for ind, val in enumerate(row_one):
+        window_start = max(ind - hf_window, 0)
+        window_end = min(ind + hf_window + odd, num_points)
+        noises[ind] = scoreatpercentile(row_one[window_start:window_end],
+                                        per=noise_perc)
+
+    def filt_func(line):
+        if len(line[0]) < min_length:
+            return False
+        snr = abs(cwt[line[0][0], line[1][0]] / noises[line[1][0]])
+        if snr < min_snr:
+            return False
+        return True
+
+    return list(filter(filt_func, ridge_lines))
+
+
+def find_peaks_cwt(vector, widths, wavelet=None, max_distances=None,
+                   gap_thresh=None, min_length=None,
+                   min_snr=1, noise_perc=10, window_size=None):
+    """
+    Find peaks in a 1-D array with wavelet transformation.
+
+    The general approach is to smooth `vector` by convolving it with
+    `wavelet(width)` for each width in `widths`. Relative maxima which
+    appear at enough length scales, and with sufficiently high SNR, are
+    accepted.
+
+    Parameters
+    ----------
+    vector : ndarray
+        1-D array in which to find the peaks.
+    widths : float or sequence
+        Single width or 1-D array-like of widths to use for calculating
+        the CWT matrix. In general,
+        this range should cover the expected width of peaks of interest.
+    wavelet : callable, optional
+        Should take two parameters and return a 1-D array to convolve
+        with `vector`. The first parameter determines the number of points
+        of the returned wavelet array, the second parameter is the scale
+        (`width`) of the wavelet. Should be normalized and symmetric.
+        Default is the ricker wavelet.
+    max_distances : ndarray, optional
+        At each row, a ridge line is only connected if the relative max at
+        row[n] is within ``max_distances[n]`` from the relative max at
+        ``row[n+1]``.  Default value is ``widths/4``.
+    gap_thresh : float, optional
+        If a relative maximum is not found within `max_distances`,
+        there will be a gap. A ridge line is discontinued if there are more
+        than `gap_thresh` points without connecting a new relative maximum.
+        Default is the first value of the widths array i.e. widths[0].
+    min_length : int, optional
+        Minimum length a ridge line needs to be acceptable.
+        Default is ``cwt.shape[0] / 4``, ie 1/4-th the number of widths.
+    min_snr : float, optional
+        Minimum SNR ratio. Default 1. The signal is the maximum CWT coefficient
+        on the largest ridge line. The noise is `noise_perc` th percentile of
+        datapoints contained within the same ridge line.
+    noise_perc : float, optional
+        When calculating the noise floor, percentile of data points
+        examined below which to consider noise. Calculated using
+        `stats.scoreatpercentile`.  Default is 10.
+    window_size : int, optional
+        Size of window to use to calculate noise floor.
+        Default is ``cwt.shape[1] / 20``.
+
+    Returns
+    -------
+    peaks_indices : ndarray
+        Indices of the locations in the `vector` where peaks were found.
+        The list is sorted.
+
+    See Also
+    --------
+    find_peaks
+        Find peaks inside a signal based on peak properties.
+
+    Notes
+    -----
+    This approach was designed for finding sharp peaks among noisy data,
+    however with proper parameter selection it should function well for
+    different peak shapes.
+
+    The algorithm is as follows:
+     1. Perform a continuous wavelet transform on `vector`, for the supplied
+        `widths`. This is a convolution of `vector` with `wavelet(width)` for
+        each width in `widths`. See `cwt`.
+     2. Identify "ridge lines" in the cwt matrix. These are relative maxima
+        at each row, connected across adjacent rows. See identify_ridge_lines
+     3. Filter the ridge_lines using filter_ridge_lines.
+
+    .. versionadded:: 0.11.0
+
+    References
+    ----------
+    .. [1] Bioinformatics (2006) 22 (17): 2059-2065.
+       :doi:`10.1093/bioinformatics/btl355`
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> xs = np.arange(0, np.pi, 0.05)
+    >>> data = np.sin(xs)
+    >>> peakind = signal.find_peaks_cwt(data, np.arange(1,10))
+    >>> peakind, xs[peakind], data[peakind]
+    ([32], array([ 1.6]), array([ 0.9995736]))
+
+    """
+    widths = np.atleast_1d(np.asarray(widths))
+
+    if gap_thresh is None:
+        gap_thresh = np.ceil(widths[0])
+    if max_distances is None:
+        max_distances = widths / 4.0
+    if wavelet is None:
+        wavelet = _ricker
+
+    cwt_dat = _cwt(vector, wavelet, widths)
+    ridge_lines = _identify_ridge_lines(cwt_dat, max_distances, gap_thresh)
+    filtered = _filter_ridge_lines(cwt_dat, ridge_lines, min_length=min_length,
+                                   window_size=window_size, min_snr=min_snr,
+                                   noise_perc=noise_perc)
+    max_locs = np.asarray([x[1][0] for x in filtered])
+    max_locs.sort()
+
+    return max_locs

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_savitzky_golay.py

@@ -0,0 +1,357 @@
+import numpy as np
+from scipy.linalg import lstsq
+from scipy._lib._util import float_factorial
+from scipy.ndimage import convolve1d  # type: ignore[attr-defined]
+from ._arraytools import axis_slice
+
+
+def savgol_coeffs(window_length, polyorder, deriv=0, delta=1.0, pos=None,
+                  use="conv"):
+    """Compute the coefficients for a 1-D Savitzky-Golay FIR filter.
+
+    Parameters
+    ----------
+    window_length : int
+        The length of the filter window (i.e., the number of coefficients).
+    polyorder : int
+        The order of the polynomial used to fit the samples.
+        `polyorder` must be less than `window_length`.
+    deriv : int, optional
+        The order of the derivative to compute. This must be a
+        nonnegative integer. The default is 0, which means to filter
+        the data without differentiating.
+    delta : float, optional
+        The spacing of the samples to which the filter will be applied.
+        This is only used if deriv > 0.
+    pos : int or None, optional
+        If pos is not None, it specifies evaluation position within the
+        window. The default is the middle of the window.
+    use : str, optional
+        Either 'conv' or 'dot'. This argument chooses the order of the
+        coefficients. The default is 'conv', which means that the
+        coefficients are ordered to be used in a convolution. With
+        use='dot', the order is reversed, so the filter is applied by
+        dotting the coefficients with the data set.
+
+    Returns
+    -------
+    coeffs : 1-D ndarray
+        The filter coefficients.
+
+    See Also
+    --------
+    savgol_filter
+
+    Notes
+    -----
+    .. versionadded:: 0.14.0
+
+    References
+    ----------
+    A. Savitzky, M. J. E. Golay, Smoothing and Differentiation of Data by
+    Simplified Least Squares Procedures. Analytical Chemistry, 1964, 36 (8),
+    pp 1627-1639.
+    Jianwen Luo, Kui Ying, and Jing Bai. 2005. Savitzky-Golay smoothing and
+    differentiation filter for even number data. Signal Process.
+    85, 7 (July 2005), 1429-1434.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal import savgol_coeffs
+    >>> savgol_coeffs(5, 2)
+    array([-0.08571429,  0.34285714,  0.48571429,  0.34285714, -0.08571429])
+    >>> savgol_coeffs(5, 2, deriv=1)
+    array([ 2.00000000e-01,  1.00000000e-01,  2.07548111e-16, -1.00000000e-01,
+           -2.00000000e-01])
+
+    Note that use='dot' simply reverses the coefficients.
+
+    >>> savgol_coeffs(5, 2, pos=3)
+    array([ 0.25714286,  0.37142857,  0.34285714,  0.17142857, -0.14285714])
+    >>> savgol_coeffs(5, 2, pos=3, use='dot')
+    array([-0.14285714,  0.17142857,  0.34285714,  0.37142857,  0.25714286])
+    >>> savgol_coeffs(4, 2, pos=3, deriv=1, use='dot')
+    array([0.45,  -0.85,  -0.65,  1.05])
+
+    `x` contains data from the parabola x = t**2, sampled at
+    t = -1, 0, 1, 2, 3.  `c` holds the coefficients that will compute the
+    derivative at the last position.  When dotted with `x` the result should
+    be 6.
+
+    >>> x = np.array([1, 0, 1, 4, 9])
+    >>> c = savgol_coeffs(5, 2, pos=4, deriv=1, use='dot')
+    >>> c.dot(x)
+    6.0
+    """
+
+    # An alternative method for finding the coefficients when deriv=0 is
+    #    t = np.arange(window_length)
+    #    unit = (t == pos).astype(int)
+    #    coeffs = np.polyval(np.polyfit(t, unit, polyorder), t)
+    # The method implemented here is faster.
+
+    # To recreate the table of sample coefficients shown in the chapter on
+    # the Savitzy-Golay filter in the Numerical Recipes book, use
+    #    window_length = nL + nR + 1
+    #    pos = nL + 1
+    #    c = savgol_coeffs(window_length, M, pos=pos, use='dot')
+
+    if polyorder >= window_length:
+        raise ValueError("polyorder must be less than window_length.")
+
+    halflen, rem = divmod(window_length, 2)
+
+    if pos is None:
+        if rem == 0:
+            pos = halflen - 0.5
+        else:
+            pos = halflen
+
+    if not (0 <= pos < window_length):
+        raise ValueError("pos must be nonnegative and less than "
+                         "window_length.")
+
+    if use not in ['conv', 'dot']:
+        raise ValueError("`use` must be 'conv' or 'dot'")
+
+    if deriv > polyorder:
+        coeffs = np.zeros(window_length)
+        return coeffs
+
+    # Form the design matrix A. The columns of A are powers of the integers
+    # from -pos to window_length - pos - 1. The powers (i.e., rows) range
+    # from 0 to polyorder. (That is, A is a vandermonde matrix, but not
+    # necessarily square.)
+    x = np.arange(-pos, window_length - pos, dtype=float)
+
+    if use == "conv":
+        # Reverse so that result can be used in a convolution.
+        x = x[::-1]
+
+    order = np.arange(polyorder + 1).reshape(-1, 1)
+    A = x ** order
+
+    # y determines which order derivative is returned.
+    y = np.zeros(polyorder + 1)
+    # The coefficient assigned to y[deriv] scales the result to take into
+    # account the order of the derivative and the sample spacing.
+    y[deriv] = float_factorial(deriv) / (delta ** deriv)
+
+    # Find the least-squares solution of A*c = y
+    coeffs, _, _, _ = lstsq(A, y)
+
+    return coeffs
+
+
+def _polyder(p, m):
+    """Differentiate polynomials represented with coefficients.
+
+    p must be a 1-D or 2-D array.  In the 2-D case, each column gives
+    the coefficients of a polynomial; the first row holds the coefficients
+    associated with the highest power. m must be a nonnegative integer.
+    (numpy.polyder doesn't handle the 2-D case.)
+    """
+
+    if m == 0:
+        result = p
+    else:
+        n = len(p)
+        if n <= m:
+            result = np.zeros_like(p[:1, ...])
+        else:
+            dp = p[:-m].copy()
+            for k in range(m):
+                rng = np.arange(n - k - 1, m - k - 1, -1)
+                dp *= rng.reshape((n - m,) + (1,) * (p.ndim - 1))
+            result = dp
+    return result
+
+
+def _fit_edge(x, window_start, window_stop, interp_start, interp_stop,
+              axis, polyorder, deriv, delta, y):
+    """
+    Given an N-d array `x` and the specification of a slice of `x` from
+    `window_start` to `window_stop` along `axis`, create an interpolating
+    polynomial of each 1-D slice, and evaluate that polynomial in the slice
+    from `interp_start` to `interp_stop`. Put the result into the
+    corresponding slice of `y`.
+    """
+
+    # Get the edge into a (window_length, -1) array.
+    x_edge = axis_slice(x, start=window_start, stop=window_stop, axis=axis)
+    if axis == 0 or axis == -x.ndim:
+        xx_edge = x_edge
+        swapped = False
+    else:
+        xx_edge = x_edge.swapaxes(axis, 0)
+        swapped = True
+    xx_edge = xx_edge.reshape(xx_edge.shape[0], -1)
+
+    # Fit the edges.  poly_coeffs has shape (polyorder + 1, -1),
+    # where '-1' is the same as in xx_edge.
+    poly_coeffs = np.polyfit(np.arange(0, window_stop - window_start),
+                             xx_edge, polyorder)
+
+    if deriv > 0:
+        poly_coeffs = _polyder(poly_coeffs, deriv)
+
+    # Compute the interpolated values for the edge.
+    i = np.arange(interp_start - window_start, interp_stop - window_start)
+    values = np.polyval(poly_coeffs, i.reshape(-1, 1)) / (delta ** deriv)
+
+    # Now put the values into the appropriate slice of y.
+    # First reshape values to match y.
+    shp = list(y.shape)
+    shp[0], shp[axis] = shp[axis], shp[0]
+    values = values.reshape(interp_stop - interp_start, *shp[1:])
+    if swapped:
+        values = values.swapaxes(0, axis)
+    # Get a view of the data to be replaced by values.
+    y_edge = axis_slice(y, start=interp_start, stop=interp_stop, axis=axis)
+    y_edge[...] = values
+
+
+def _fit_edges_polyfit(x, window_length, polyorder, deriv, delta, axis, y):
+    """
+    Use polynomial interpolation of x at the low and high ends of the axis
+    to fill in the halflen values in y.
+
+    This function just calls _fit_edge twice, once for each end of the axis.
+    """
+    halflen = window_length // 2
+    _fit_edge(x, 0, window_length, 0, halflen, axis,
+              polyorder, deriv, delta, y)
+    n = x.shape[axis]
+    _fit_edge(x, n - window_length, n, n - halflen, n, axis,
+              polyorder, deriv, delta, y)
+
+
+def savgol_filter(x, window_length, polyorder, deriv=0, delta=1.0,
+                  axis=-1, mode='interp', cval=0.0):
+    """ Apply a Savitzky-Golay filter to an array.
+
+    This is a 1-D filter. If `x`  has dimension greater than 1, `axis`
+    determines the axis along which the filter is applied.
+
+    Parameters
+    ----------
+    x : array_like
+        The data to be filtered. If `x` is not a single or double precision
+        floating point array, it will be converted to type ``numpy.float64``
+        before filtering.
+    window_length : int
+        The length of the filter window (i.e., the number of coefficients).
+        If `mode` is 'interp', `window_length` must be less than or equal
+        to the size of `x`.
+    polyorder : int
+        The order of the polynomial used to fit the samples.
+        `polyorder` must be less than `window_length`.
+    deriv : int, optional
+        The order of the derivative to compute. This must be a
+        nonnegative integer. The default is 0, which means to filter
+        the data without differentiating.
+    delta : float, optional
+        The spacing of the samples to which the filter will be applied.
+        This is only used if deriv > 0. Default is 1.0.
+    axis : int, optional
+        The axis of the array `x` along which the filter is to be applied.
+        Default is -1.
+    mode : str, optional
+        Must be 'mirror', 'constant', 'nearest', 'wrap' or 'interp'. This
+        determines the type of extension to use for the padded signal to
+        which the filter is applied.  When `mode` is 'constant', the padding
+        value is given by `cval`.  See the Notes for more details on 'mirror',
+        'constant', 'wrap', and 'nearest'.
+        When the 'interp' mode is selected (the default), no extension
+        is used.  Instead, a degree `polyorder` polynomial is fit to the
+        last `window_length` values of the edges, and this polynomial is
+        used to evaluate the last `window_length // 2` output values.
+    cval : scalar, optional
+        Value to fill past the edges of the input if `mode` is 'constant'.
+        Default is 0.0.
+
+    Returns
+    -------
+    y : ndarray, same shape as `x`
+        The filtered data.
+
+    See Also
+    --------
+    savgol_coeffs
+
+    Notes
+    -----
+    Details on the `mode` options:
+
+        'mirror':
+            Repeats the values at the edges in reverse order. The value
+            closest to the edge is not included.
+        'nearest':
+            The extension contains the nearest input value.
+        'constant':
+            The extension contains the value given by the `cval` argument.
+        'wrap':
+            The extension contains the values from the other end of the array.
+
+    For example, if the input is [1, 2, 3, 4, 5, 6, 7, 8], and
+    `window_length` is 7, the following shows the extended data for
+    the various `mode` options (assuming `cval` is 0)::
+
+        mode       |   Ext   |         Input          |   Ext
+        -----------+---------+------------------------+---------
+        'mirror'   | 4  3  2 | 1  2  3  4  5  6  7  8 | 7  6  5
+        'nearest'  | 1  1  1 | 1  2  3  4  5  6  7  8 | 8  8  8
+        'constant' | 0  0  0 | 1  2  3  4  5  6  7  8 | 0  0  0
+        'wrap'     | 6  7  8 | 1  2  3  4  5  6  7  8 | 1  2  3
+
+    .. versionadded:: 0.14.0
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.signal import savgol_filter
+    >>> np.set_printoptions(precision=2)  # For compact display.
+    >>> x = np.array([2, 2, 5, 2, 1, 0, 1, 4, 9])
+
+    Filter with a window length of 5 and a degree 2 polynomial.  Use
+    the defaults for all other parameters.
+
+    >>> savgol_filter(x, 5, 2)
+    array([1.66, 3.17, 3.54, 2.86, 0.66, 0.17, 1.  , 4.  , 9.  ])
+
+    Note that the last five values in x are samples of a parabola, so
+    when mode='interp' (the default) is used with polyorder=2, the last
+    three values are unchanged. Compare that to, for example,
+    `mode='nearest'`:
+
+    >>> savgol_filter(x, 5, 2, mode='nearest')
+    array([1.74, 3.03, 3.54, 2.86, 0.66, 0.17, 1.  , 4.6 , 7.97])
+
+    """
+    if mode not in ["mirror", "constant", "nearest", "interp", "wrap"]:
+        raise ValueError("mode must be 'mirror', 'constant', 'nearest' "
+                         "'wrap' or 'interp'.")
+
+    x = np.asarray(x)
+    # Ensure that x is either single or double precision floating point.
+    if x.dtype != np.float64 and x.dtype != np.float32:
+        x = x.astype(np.float64)
+
+    coeffs = savgol_coeffs(window_length, polyorder, deriv=deriv, delta=delta)
+
+    if mode == "interp":
+        if window_length > x.shape[axis]:
+            raise ValueError("If mode is 'interp', window_length must be less "
+                             "than or equal to the size of x.")
+
+        # Do not pad. Instead, for the elements within `window_length // 2`
+        # of the ends of the sequence, use the polynomial that is fitted to
+        # the last `window_length` elements.
+        y = convolve1d(x, coeffs, axis=axis, mode="constant")
+        _fit_edges_polyfit(x, window_length, polyorder, deriv, delta, axis, y)
+    else:
+        # Any mode other than 'interp' is passed on to ndimage.convolve1d.
+        y = convolve1d(x, coeffs, axis=axis, mode=mode, cval=cval)
+
+    return y

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_short_time_fft.py

@@ -0,0 +1,1710 @@
+"""Implementation of an FFT-based Short-time Fourier Transform. """
+
+# Implementation Notes for this file (as of 2023-07)
+# --------------------------------------------------
+# * MyPy version 1.1.1 does not seem to support decorated property methods
+#   properly. Hence, applying ``@property`` to methods decorated with `@cache``
+#   (as tried with the ``lower_border_end`` method) causes a mypy error when
+#   accessing it as an index (e.g., ``SFT.lower_border_end[0]``).
+# * Since the method `stft` and `istft` have identical names as the legacy
+#   functions in the signal module, referencing them as HTML link in the
+#   docstrings has to be done by an explicit `~ShortTimeFFT.stft` instead of an
+#   ambiguous `stft` (The ``~`` hides the class / module name).
+# * The HTML documentation currently renders each method/property on a separate
+#   page without reference to the parent class. Thus, a link to `ShortTimeFFT`
+#   was added to the "See Also" section of each method/property. These links
+#   can be removed, when SciPy updates ``pydata-sphinx-theme`` to >= 0.13.3
+#   (currently 0.9). Consult Issue 18512 and PR 16660 for further details.
+#
+
+# Provides typing union operator ``|`` in Python 3.9:
+# Linter does not allow to import ``Generator`` from ``typing`` module:
+from collections.abc import Generator, Callable
+from functools import cache, lru_cache, partial
+from typing import get_args, Literal
+
+import numpy as np
+
+import scipy.fft as fft_lib
+from scipy.signal import detrend
+from scipy.signal.windows import get_window
+
+__all__ = ['ShortTimeFFT']
+
+
+#: Allowed values for parameter `padding` of method `ShortTimeFFT.stft()`:
+PAD_TYPE = Literal['zeros', 'edge', 'even', 'odd']
+
+#: Allowed values for property `ShortTimeFFT.fft_mode`:
+FFT_MODE_TYPE = Literal['twosided', 'centered', 'onesided', 'onesided2X']
+
+
+def _calc_dual_canonical_window(win: np.ndarray, hop: int) -> np.ndarray:
+    """Calculate canonical dual window for 1d window `win` and a time step
+    of `hop` samples.
+
+    A ``ValueError`` is raised, if the inversion fails.
+
+    This is a separate function not a method, since it is also used in the
+    class method ``ShortTimeFFT.from_dual()``.
+    """
+    if hop > len(win):
+        raise ValueError(f"{hop=} is larger than window length of {len(win)}" +
+                         " => STFT not invertible!")
+    if issubclass(win.dtype.type, np.integer):
+        raise ValueError("Parameter 'win' cannot be of integer type, but " +
+                         f"{win.dtype=} => STFT not invertible!")
+        # The calculation of `relative_resolution` does not work for ints.
+        # Furthermore, `win / DD` casts the integers away, thus an implicit
+        # cast is avoided, which can always cause confusion when using 32-Bit
+        # floats.
+
+    w2 = win.real**2 + win.imag**2  # win*win.conj() does not ensure w2 is real
+    DD = w2.copy()
+    for k_ in range(hop, len(win), hop):
+        DD[k_:] += w2[:-k_]
+        DD[:-k_] += w2[k_:]
+
+    # check DD > 0:
+    relative_resolution = np.finfo(win.dtype).resolution * max(DD)
+    if not np.all(DD >= relative_resolution):
+        raise ValueError("Short-time Fourier Transform not invertible!")
+
+    return win / DD
+
+
+# noinspection PyShadowingNames
+class ShortTimeFFT:
+    r"""Provide a parametrized discrete Short-time Fourier transform (stft)
+    and its inverse (istft).
+
+    .. currentmodule:: scipy.signal.ShortTimeFFT
+
+    The `~ShortTimeFFT.stft` calculates sequential FFTs by sliding a
+    window (`win`) over an input signal by `hop` increments. It can be used to
+    quantify the change of the spectrum over time.
+
+    The `~ShortTimeFFT.stft` is represented by a complex-valued matrix S[q,p]
+    where the p-th column represents an FFT with the window centered at the
+    time t[p] = p * `delta_t` = p * `hop` * `T` where `T` is  the sampling
+    interval of the input signal. The q-th row represents the values at the
+    frequency f[q] = q * `delta_f` with `delta_f` = 1 / (`mfft` * `T`) being
+    the bin width of the FFT.
+
+    The inverse STFT `~ShortTimeFFT.istft` is calculated by reversing the steps
+    of the STFT: Take the IFFT of the p-th slice of S[q,p] and multiply the
+    result with the so-called dual window (see `dual_win`). Shift the result by
+    p * `delta_t` and add the result to previous shifted results to reconstruct
+    the signal. If only the dual window is known and the STFT is invertible,
+    `from_dual` can be used to instantiate this class.
+
+    Due to the convention of time t = 0 being at the first sample of the input
+    signal, the STFT values typically have negative time slots. Hence,
+    negative indexes like `p_min` or `k_min` do not indicate counting
+    backwards from an array's end like in standard Python indexing but being
+    left of t = 0.
+
+    More detailed information can be found in the :ref:`tutorial_stft` section
+    of the :ref:`user_guide`.
+
+    Note that all parameters of the initializer, except `scale_to` (which uses
+    `scaling`) have identical named attributes.
+
+    Parameters
+    ----------
+    win : np.ndarray
+        The window must be a real- or complex-valued 1d array.
+    hop : int
+        The increment in samples, by which the window is shifted in each step.
+    fs : float
+        Sampling frequency of input signal and window. Its relation to the
+        sampling interval `T` is ``T = 1 / fs``.
+    fft_mode : 'twosided', 'centered', 'onesided', 'onesided2X'
+        Mode of FFT to be used (default 'onesided').
+        See property `fft_mode` for details.
+    mfft: int | None
+        Length of the FFT used, if a zero padded FFT is desired.
+        If ``None`` (default), the length of the window `win` is used.
+    dual_win : np.ndarray | None
+        The dual window of `win`. If set to ``None``, it is calculated if
+        needed.
+    scale_to : 'magnitude', 'psd' | None
+        If not ``None`` (default) the window function is scaled, so each STFT
+        column represents  either a 'magnitude' or a power spectral density
+        ('psd') spectrum. This parameter sets the property `scaling` to the
+        same value. See method `scale_to` for details.
+    phase_shift : int | None
+        If set, add a linear phase `phase_shift` / `mfft` * `f` to each
+        frequency `f`. The default value 0 ensures that there is no phase shift
+        on the zeroth slice (in which t=0 is centered). See property
+        `phase_shift` for more details.
+
+    Examples
+    --------
+    The following example shows the magnitude of the STFT of a sine with
+    varying frequency :math:`f_i(t)` (marked by a red dashed line in the plot):
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.signal import ShortTimeFFT
+    >>> from scipy.signal.windows import gaussian
+    ...
+    >>> T_x, N = 1 / 20, 1000  # 20 Hz sampling rate for 50 s signal
+    >>> t_x = np.arange(N) * T_x  # time indexes for signal
+    >>> f_i = 1 * np.arctan((t_x - t_x[N // 2]) / 2) + 5  # varying frequency
+    >>> x = np.sin(2*np.pi*np.cumsum(f_i)*T_x) # the signal
+
+    The utilized Gaussian window is 50 samples or 2.5 s long. The parameter
+    ``mfft=200`` in `ShortTimeFFT` causes the spectrum to be oversampled
+    by a factor of 4:
+
+    >>> g_std = 8  # standard deviation for Gaussian window in samples
+    >>> w = gaussian(50, std=g_std, sym=True)  # symmetric Gaussian window
+    >>> SFT = ShortTimeFFT(w, hop=10, fs=1/T_x, mfft=200, scale_to='magnitude')
+    >>> Sx = SFT.stft(x)  # perform the STFT
+
+    In the plot, the time extent of the signal `x` is marked by vertical dashed
+    lines. Note that the SFT produces values outside the time range of `x`. The
+    shaded areas on the left and the right indicate border effects caused
+    by  the window slices in that area not fully being inside time range of
+    `x`:
+
+    >>> fig1, ax1 = plt.subplots(figsize=(6., 4.))  # enlarge plot a bit
+    >>> t_lo, t_hi = SFT.extent(N)[:2]  # time range of plot
+    >>> ax1.set_title(rf"STFT ({SFT.m_num*SFT.T:g}$\,s$ Gaussian window, " +
+    ...               rf"$\sigma_t={g_std*SFT.T}\,$s)")
+    >>> ax1.set(xlabel=f"Time $t$ in seconds ({SFT.p_num(N)} slices, " +
+    ...                rf"$\Delta t = {SFT.delta_t:g}\,$s)",
+    ...         ylabel=f"Freq. $f$ in Hz ({SFT.f_pts} bins, " +
+    ...                rf"$\Delta f = {SFT.delta_f:g}\,$Hz)",
+    ...         xlim=(t_lo, t_hi))
+    ...
+    >>> im1 = ax1.imshow(abs(Sx), origin='lower', aspect='auto',
+    ...                  extent=SFT.extent(N), cmap='viridis')
+    >>> ax1.plot(t_x, f_i, 'r--', alpha=.5, label='$f_i(t)$')
+    >>> fig1.colorbar(im1, label="Magnitude $|S_x(t, f)|$")
+    ...
+    >>> # Shade areas where window slices stick out to the side:
+    >>> for t0_, t1_ in [(t_lo, SFT.lower_border_end[0] * SFT.T),
+    ...                  (SFT.upper_border_begin(N)[0] * SFT.T, t_hi)]:
+    ...     ax1.axvspan(t0_, t1_, color='w', linewidth=0, alpha=.2)
+    >>> for t_ in [0, N * SFT.T]:  # mark signal borders with vertical line:
+    ...     ax1.axvline(t_, color='y', linestyle='--', alpha=0.5)
+    >>> ax1.legend()
+    >>> fig1.tight_layout()
+    >>> plt.show()
+
+    Reconstructing the signal with the `~ShortTimeFFT.istft` is
+    straightforward, but note that the length of `x1` should be specified,
+    since the SFT length increases in `hop` steps:
+
+    >>> SFT.invertible  # check if invertible
+    True
+    >>> x1 = SFT.istft(Sx, k1=N)
+    >>> np.allclose(x, x1)
+    True
+
+    It is possible to calculate the SFT of signal parts:
+
+    >>> p_q = SFT.nearest_k_p(N // 2)
+    >>> Sx0 = SFT.stft(x[:p_q])
+    >>> Sx1 = SFT.stft(x[p_q:])
+
+    When assembling sequential STFT parts together, the overlap needs to be
+    considered:
+
+    >>> p0_ub = SFT.upper_border_begin(p_q)[1] - SFT.p_min
+    >>> p1_le = SFT.lower_border_end[1] - SFT.p_min
+    >>> Sx01 = np.hstack((Sx0[:, :p0_ub],
+    ...                   Sx0[:, p0_ub:] + Sx1[:, :p1_le],
+    ...                   Sx1[:, p1_le:]))
+    >>> np.allclose(Sx01, Sx)  # Compare with SFT of complete signal
+    True
+
+    It is also possible to calculate the `itsft` for signal parts:
+
+    >>> y_p = SFT.istft(Sx, N//3, N//2)
+    >>> np.allclose(y_p, x[N//3:N//2])
+    True
+
+    """
+    # immutable attributes (only have getters but no setters):
+    _win: np.ndarray  # window
+    _dual_win: np.ndarray | None = None  # canonical dual window
+    _hop: int  # Step of STFT in number of samples
+
+    # mutable attributes:
+    _fs: float  # sampling frequency of input signal and window
+    _fft_mode: FFT_MODE_TYPE = 'onesided'  # Mode of FFT to use
+    _mfft: int  # length of FFT used - defaults to len(win)
+    _scaling: Literal['magnitude', 'psd'] | None = None  # Scaling of _win
+    _phase_shift: int | None  # amount to shift phase of FFT in samples
+
+    # attributes for caching calculated values:
+    _fac_mag: float | None = None
+    _fac_psd: float | None = None
+    _lower_border_end: tuple[int, int] | None = None
+
+    def __init__(self, win: np.ndarray, hop: int, fs: float, *,
+                 fft_mode: FFT_MODE_TYPE = 'onesided',
+                 mfft: int | None = None,
+                 dual_win: np.ndarray | None = None,
+                 scale_to: Literal['magnitude', 'psd'] | None = None,
+                 phase_shift: int | None = 0):
+        if not (win.ndim == 1 and win.size > 0):
+            raise ValueError(f"Parameter win must be 1d, but {win.shape=}!")
+        if not all(np.isfinite(win)):
+            raise ValueError("Parameter win must have finite entries!")
+        if not (hop >= 1 and isinstance(hop, int)):
+            raise ValueError(f"Parameter {hop=} is not an integer >= 1!")
+        self._win, self._hop, self.fs = win, hop, fs
+
+        self.mfft = len(win) if mfft is None else mfft
+
+        if dual_win is not None:
+            if dual_win.shape != win.shape:
+                raise ValueError(f"{dual_win.shape=} must equal {win.shape=}!")
+            if not all(np.isfinite(dual_win)):
+                raise ValueError("Parameter dual_win must be a finite array!")
+        self._dual_win = dual_win  # needs to be set before scaling
+
+        if scale_to is not None:  # needs to be set before fft_mode
+            self.scale_to(scale_to)
+
+        self.fft_mode, self.phase_shift = fft_mode, phase_shift
+
+    @classmethod
+    def from_dual(cls, dual_win: np.ndarray, hop: int, fs: float, *,
+                  fft_mode: FFT_MODE_TYPE = 'onesided',
+                  mfft: int | None = None,
+                  scale_to: Literal['magnitude', 'psd'] | None = None,
+                  phase_shift: int | None = 0):
+        r"""Instantiate a `ShortTimeFFT` by only providing a dual window.
+
+        If an STFT is invertible, it is possible to calculate the window `win`
+        from a given dual window `dual_win`. All other parameters have the
+        same meaning as in the initializer of `ShortTimeFFT`.
+
+        As explained in the :ref:`tutorial_stft` section of the
+        :ref:`user_guide`, an invertible STFT can be interpreted as series
+        expansion of time-shifted and frequency modulated dual windows. E.g.,
+        the series coefficient S[q,p] belongs to the term, which shifted
+        `dual_win` by p * `delta_t` and multiplied it by
+        exp( 2 * j * pi * t * q * `delta_f`).
+
+
+        Examples
+        --------
+        The following example discusses decomposing a signal into time- and
+        frequency-shifted Gaussians. A Gaussian with standard deviation of
+        one made up of 51 samples will be used:
+
+        >>> import numpy as np
+        >>> import matplotlib.pyplot as plt
+        >>> from scipy.signal import ShortTimeFFT
+        >>> from scipy.signal.windows import gaussian
+        ...
+        >>> T, N = 0.1, 51
+        >>> d_win = gaussian(N, std=1/T, sym=True)  # symmetric Gaussian window
+        >>> t = T * (np.arange(N) - N//2)
+        ...
+        >>> fg1, ax1 = plt.subplots()
+        >>> ax1.set_title(r"Dual Window: Gaussian with $\sigma_t=1$")
+        >>> ax1.set(xlabel=f"Time $t$ in seconds ({N} samples, $T={T}$ s)",
+        ...        xlim=(t[0], t[-1]), ylim=(0, 1.1*max(d_win)))
+        >>> ax1.plot(t, d_win, 'C0-')
+
+        The following plot with the overlap of 41, 11 and 2 samples show how
+        the `hop` interval affects the shape of the window `win`:
+
+        >>> fig2, axx = plt.subplots(3, 1, sharex='all')
+        ...
+        >>> axx[0].set_title(r"Windows for hop$\in\{10, 40, 49\}$")
+        >>> for c_, h_ in enumerate([10, 40, 49]):
+        ...     SFT = ShortTimeFFT.from_dual(d_win, h_, 1/T)
+        ...     axx[c_].plot(t + h_ * T, SFT.win, 'k--', alpha=.3, label=None)
+        ...     axx[c_].plot(t - h_ * T, SFT.win, 'k:', alpha=.3, label=None)
+        ...     axx[c_].plot(t, SFT.win, f'C{c_+1}',
+        ...                     label=r"$\Delta t=%0.1f\,$s" % SFT.delta_t)
+        ...     axx[c_].set_ylim(0, 1.1*max(SFT.win))
+        ...     axx[c_].legend(loc='center')
+        >>> axx[-1].set(xlabel=f"Time $t$ in seconds ({N} samples, $T={T}$ s)",
+        ...             xlim=(t[0], t[-1]))
+        >>> plt.show()
+
+        Beside the window `win` centered at t = 0 the previous (t = -`delta_t`)
+        and following window (t = `delta_t`) are depicted. It can be seen that
+        for small `hop` intervals, the window is compact and smooth, having a
+        good time-frequency concentration in the STFT. For the large `hop`
+        interval of 4.9 s, the window has small values around t = 0, which are
+        not covered by the overlap of the adjacent windows, which could lead to
+        numeric inaccuracies. Furthermore, the peaky shape at the beginning and
+        the end of the window points to a higher bandwidth, resulting in a
+        poorer time-frequency resolution of the STFT.
+        Hence, the choice of the `hop` interval will be a compromise between
+        a time-frequency resolution and memory requirements demanded by small
+        `hop` sizes.
+
+        See Also
+        --------
+        from_window: Create instance by wrapping `get_window`.
+        ShortTimeFFT: Create instance using standard initializer.
+        """
+        win = _calc_dual_canonical_window(dual_win, hop)
+        return cls(win=win, hop=hop, fs=fs, fft_mode=fft_mode, mfft=mfft,
+                   dual_win=dual_win, scale_to=scale_to,
+                   phase_shift=phase_shift)
+
+    @classmethod
+    def from_window(cls, win_param: str | tuple | float,
+                    fs: float, nperseg: int, noverlap: int, *,
+                    symmetric_win: bool = False,
+                    fft_mode: FFT_MODE_TYPE = 'onesided',
+                    mfft: int | None = None,
+                    scale_to: Literal['magnitude', 'psd'] | None = None,
+                    phase_shift: int | None = 0):
+        """Instantiate `ShortTimeFFT` by using `get_window`.
+
+        The method `get_window` is used to create a window of length
+        `nperseg`. The parameter names `noverlap`, and `nperseg` are used here,
+        since they more inline with other classical STFT libraries.
+
+        Parameters
+        ----------
+        win_param: Union[str, tuple, float],
+            Parameters passed to `get_window`. For windows with no parameters,
+            it may be a string (e.g., ``'hann'``), for parametrized windows a
+            tuple, (e.g., ``('gaussian', 2.)``) or a single float specifying
+            the shape parameter of a kaiser window (i.e. ``4.``  and
+            ``('kaiser', 4.)`` are equal. See `get_window` for more details.
+        fs : float
+            Sampling frequency of input signal. Its relation to the
+            sampling interval `T` is ``T = 1 / fs``.
+        nperseg: int
+            Window length in samples, which corresponds to the `m_num`.
+        noverlap: int
+            Window overlap in samples. It relates to the `hop` increment by
+            ``hop = npsereg - noverlap``.
+        symmetric_win: bool
+            If ``True`` then a symmetric window is generated, else a periodic
+            window is generated (default). Though symmetric windows seem for
+            most applications to be more sensible, the default of a periodic
+            windows was chosen to correspond to the default of `get_window`.
+        fft_mode : 'twosided', 'centered', 'onesided', 'onesided2X'
+            Mode of FFT to be used (default 'onesided').
+            See property `fft_mode` for details.
+        mfft: int | None
+            Length of the FFT used, if a zero padded FFT is desired.
+            If ``None`` (default), the length of the window `win` is used.
+        scale_to : 'magnitude', 'psd' | None
+            If not ``None`` (default) the window function is scaled, so each
+            STFT column represents  either a 'magnitude' or a power spectral
+            density ('psd') spectrum. This parameter sets the property
+            `scaling` to the same value. See method `scale_to` for details.
+        phase_shift : int | None
+            If set, add a linear phase `phase_shift` / `mfft` * `f` to each
+            frequency `f`. The default value 0 ensures that there is no phase
+            shift on the zeroth slice (in which t=0 is centered). See property
+            `phase_shift` for more details.
+
+        Examples
+        --------
+        The following instances ``SFT0`` and ``SFT1`` are equivalent:
+
+        >>> from scipy.signal import ShortTimeFFT, get_window
+        >>> nperseg = 9  # window length
+        >>> w = get_window(('gaussian', 2.), nperseg)
+        >>> fs = 128  # sampling frequency
+        >>> hop = 3  # increment of STFT time slice
+        >>> SFT0 = ShortTimeFFT(w, hop, fs=fs)
+        >>> SFT1 = ShortTimeFFT.from_window(('gaussian', 2.), fs, nperseg,
+        ...                                 noverlap=nperseg-hop)
+
+        See Also
+        --------
+        scipy.signal.get_window: Return a window of a given length and type.
+        from_dual: Create instance using dual window.
+        ShortTimeFFT: Create instance using standard initializer.
+        """
+        win = get_window(win_param, nperseg, fftbins=not symmetric_win)
+        return cls(win, hop=nperseg-noverlap, fs=fs, fft_mode=fft_mode,
+                   mfft=mfft, scale_to=scale_to, phase_shift=phase_shift)
+
+    @property
+    def win(self) -> np.ndarray:
+        """Window function as real- or complex-valued 1d array.
+
+        This attribute is read only, since `dual_win` depends on it.
+
+        See Also
+        --------
+        dual_win: Canonical dual window.
+        m_num: Number of samples in window `win`.
+        m_num_mid: Center index of window `win`.
+        mfft: Length of input for the FFT used - may be larger than `m_num`.
+        hop: ime increment in signal samples for sliding window.
+        win: Window function as real- or complex-valued 1d array.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self._win
+
+    @property
+    def hop(self) -> int:
+        """Time increment in signal samples for sliding window.
+
+        This attribute is read only, since `dual_win` depends on it.
+
+        See Also
+        --------
+        delta_t: Time increment of STFT (``hop*T``)
+        m_num: Number of samples in window `win`.
+        m_num_mid: Center index of window `win`.
+        mfft: Length of input for the FFT used - may be larger than `m_num`.
+        T: Sampling interval of input signal and of the window.
+        win: Window function as real- or complex-valued 1d array.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self._hop
+
+    @property
+    def T(self) -> float:
+        """Sampling interval of input signal and of the window.
+
+        A ``ValueError`` is raised if it is set to a non-positive value.
+
+        See Also
+        --------
+        delta_t: Time increment of STFT (``hop*T``)
+        hop: Time increment in signal samples for sliding window.
+        fs: Sampling frequency (being ``1/T``)
+        t: Times of STFT for an input signal with `n` samples.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return 1 / self._fs
+
+    @T.setter
+    def T(self, v: float):
+        """Sampling interval of input signal and of the window.
+
+        A ``ValueError`` is raised if it is set to a non-positive value.
+        """
+        if not (v > 0):
+            raise ValueError(f"Sampling interval T={v} must be positive!")
+        self._fs = 1 / v
+
+    @property
+    def fs(self) -> float:
+        """Sampling frequency of input signal and of the window.
+
+        The sampling frequency is the inverse of the sampling interval `T`.
+        A ``ValueError`` is raised if it is set to a non-positive value.
+
+        See Also
+        --------
+        delta_t: Time increment of STFT (``hop*T``)
+        hop: Time increment in signal samples for sliding window.
+        T: Sampling interval of input signal and of the window (``1/fs``).
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self._fs
+
+    @fs.setter
+    def fs(self, v: float):
+        """Sampling frequency of input signal and of the window.
+
+        The sampling frequency is the inverse of the sampling interval `T`.
+        A ``ValueError`` is raised if it is set to a non-positive value.
+        """
+        if not (v > 0):
+            raise ValueError(f"Sampling frequency fs={v} must be positive!")
+        self._fs = v
+
+    @property
+    def fft_mode(self) -> FFT_MODE_TYPE:
+        """Mode of utilized FFT ('twosided', 'centered', 'onesided' or
+        'onesided2X').
+
+        It can have the following values:
+
+        'twosided':
+            Two-sided FFT, where values for the negative frequencies are in
+            upper half of the array. Corresponds to :func:`~scipy.fft.fft()`.
+        'centered':
+            Two-sided FFT with the values being ordered along monotonically
+            increasing frequencies. Corresponds to applying
+            :func:`~scipy.fft.fftshift()` to :func:`~scipy.fft.fft()`.
+        'onesided':
+            Calculates only values for non-negative frequency values.
+            Corresponds to :func:`~scipy.fft.rfft()`.
+        'onesided2X':
+            Like `onesided`, but the non-zero frequencies are doubled if
+            `scaling` is set to 'magnitude' or multiplied by ``sqrt(2)`` if
+            set to 'psd'. If `scaling` is ``None``, setting `fft_mode` to
+            `onesided2X` is not allowed.
+            If the FFT length `mfft` is even, the last FFT value is not paired,
+            and thus it is not scaled.
+
+        Note that `onesided` and `onesided2X` do not work for complex-valued signals or
+        complex-valued windows. Furthermore, the frequency values can be obtained by
+        reading the `f` property, and the number of samples by accessing the `f_pts`
+        property.
+
+        See Also
+        --------
+        delta_f: Width of the frequency bins of the STFT.
+        f: Frequencies values of the STFT.
+        f_pts: Width of the frequency bins of the STFT.
+        onesided_fft: True if a one-sided FFT is used.
+        scaling: Normalization applied to the window function
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self._fft_mode
+
+    @fft_mode.setter
+    def fft_mode(self, t: FFT_MODE_TYPE):
+        """Set mode of FFT.
+
+        Allowed values are 'twosided', 'centered', 'onesided', 'onesided2X'.
+        See the property `fft_mode` for more details.
+        """
+        if t not in (fft_mode_types := get_args(FFT_MODE_TYPE)):
+            raise ValueError(f"fft_mode='{t}' not in {fft_mode_types}!")
+
+        if t in {'onesided', 'onesided2X'} and np.iscomplexobj(self.win):
+            raise ValueError(f"One-sided spectra, i.e., fft_mode='{t}', " +
+                             "are not allowed for complex-valued windows!")
+
+        if t == 'onesided2X' and self.scaling is None:
+            raise ValueError(f"For scaling is None, fft_mode='{t}' is invalid!"
+                             "Do scale_to('psd') or scale_to('magnitude')!")
+        self._fft_mode = t
+
+    @property
+    def mfft(self) -> int:
+        """Length of input for the FFT used - may be larger than window
+        length `m_num`.
+
+        If not set, `mfft` defaults to the window length `m_num`.
+
+        See Also
+        --------
+        f_pts: Number of points along the frequency axis.
+        f: Frequencies values of the STFT.
+        m_num: Number of samples in window `win`.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self._mfft
+
+    @mfft.setter
+    def mfft(self, n_: int):
+        """Setter for the length of FFT utilized.
+
+        See the property `mfft` for further details.
+        """
+        if not (n_ >= self.m_num):
+            raise ValueError(f"Attribute mfft={n_} needs to be at least the " +
+                             f"window length m_num={self.m_num}!")
+        self._mfft = n_
+
+    @property
+    def scaling(self) -> Literal['magnitude', 'psd'] | None:
+        """Normalization applied to the window function
+        ('magnitude', 'psd' or ``None``).
+
+        If not ``None``, the FFTs can be either interpreted as a magnitude or
+        a power spectral density spectrum.
+
+        The window function can be scaled by calling the `scale_to` method,
+        or it is set by the initializer parameter ``scale_to``.
+
+        See Also
+        --------
+        fac_magnitude: Scaling factor for to a magnitude spectrum.
+        fac_psd: Scaling factor for to  a power spectral density spectrum.
+        fft_mode: Mode of utilized FFT
+        scale_to: Scale window to obtain 'magnitude' or 'psd' scaling.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self._scaling
+
+    def scale_to(self, scaling: Literal['magnitude', 'psd']):
+        """Scale window to obtain 'magnitude' or 'psd' scaling for the STFT.
+
+        The window of a 'magnitude' spectrum has an integral of one, i.e., unit
+        area for non-negative windows. This ensures that absolute the values of
+        spectrum does not change if the length of the window changes (given
+        the input signal is stationary).
+
+        To represent the power spectral density ('psd') for varying length
+        windows the area of the absolute square of the window needs to be
+        unity.
+
+        The `scaling` property shows the current scaling. The properties
+        `fac_magnitude` and `fac_psd` show the scaling factors required to
+        scale the STFT values to a magnitude or a psd spectrum.
+
+        This method is called, if the initializer parameter `scale_to` is set.
+
+        See Also
+        --------
+        fac_magnitude: Scaling factor for to  a magnitude spectrum.
+        fac_psd: Scaling factor for to  a power spectral density spectrum.
+        fft_mode: Mode of utilized FFT
+        scaling: Normalization applied to the window function.
+        ShortTimeFFT: Class this method belongs to.
+        """
+        if scaling not in (scaling_values := {'magnitude', 'psd'}):
+            raise ValueError(f"{scaling=} not in {scaling_values}!")
+        if self._scaling == scaling:  # do nothing
+            return
+
+        s_fac = self.fac_psd if scaling == 'psd' else self.fac_magnitude
+        self._win = self._win * s_fac
+        if self._dual_win is not None:
+            self._dual_win = self._dual_win / s_fac
+        self._fac_mag, self._fac_psd = None, None  # reset scaling factors
+        self._scaling = scaling
+
+    @property
+    def phase_shift(self) -> int | None:
+        """If set, add linear phase `phase_shift` / `mfft` * `f` to each FFT
+        slice of frequency `f`.
+
+        Shifting (more precisely `rolling`) an `mfft`-point FFT input by
+        `phase_shift` samples results in a multiplication of the output by
+        ``np.exp(2j*np.pi*q*phase_shift/mfft)`` at the frequency q * `delta_f`.
+
+        The default value 0 ensures that there is no phase shift on the
+        zeroth slice (in which t=0 is centered).
+        No phase shift (``phase_shift is None``) is equivalent to
+        ``phase_shift = -mfft//2``. In this case slices are not shifted
+        before calculating the FFT.
+
+        The absolute value of `phase_shift` is limited to be less than `mfft`.
+
+        See Also
+        --------
+        delta_f: Width of the frequency bins of the STFT.
+        f: Frequencies values of the STFT.
+        mfft: Length of input for the FFT used
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self._phase_shift
+
+    @phase_shift.setter
+    def phase_shift(self, v: int | None):
+        """The absolute value of the phase shift needs to be less than mfft
+        samples.
+
+        See the `phase_shift` getter method for more details.
+        """
+        if v is None:
+            self._phase_shift = v
+            return
+        if not isinstance(v, int):
+            raise ValueError(f"phase_shift={v} has the unit samples. Hence " +
+                             "it needs to be an int or it may be None!")
+        if not (-self.mfft < v < self.mfft):
+            raise ValueError("-mfft < phase_shift < mfft does not hold " +
+                             f"for mfft={self.mfft}, phase_shift={v}!")
+        self._phase_shift = v
+
+    def _x_slices(self, x: np.ndarray, k_off: int, p0: int, p1: int,
+                  padding: PAD_TYPE) -> Generator[np.ndarray, None, None]:
+        """Generate signal slices along last axis of `x`.
+
+        This method is only used by `stft_detrend`. The parameters are
+        described in `~ShortTimeFFT.stft`.
+        """
+        if padding not in (padding_types := get_args(PAD_TYPE)):
+            raise ValueError(f"Parameter {padding=} not in {padding_types}!")
+        pad_kws: dict[str, dict] = {  # possible keywords to pass to np.pad:
+            'zeros': dict(mode='constant', constant_values=(0, 0)),
+            'edge': dict(mode='edge'),
+            'even': dict(mode='reflect', reflect_type='even'),
+            'odd': dict(mode='reflect', reflect_type='odd'),
+           }  # typing of pad_kws is needed to make mypy happy
+
+        n, n1 = x.shape[-1], (p1 - p0) * self.hop
+        k0 = p0 * self.hop - self.m_num_mid + k_off  # start sample
+        k1 = k0 + n1 + self.m_num  # end sample
+
+        i0, i1 = max(k0, 0), min(k1, n)  # indexes to shorten x
+        # dimensions for padding x:
+        pad_width = [(0, 0)] * (x.ndim-1) + [(-min(k0, 0), max(k1 - n, 0))]
+
+        x1 = np.pad(x[..., i0:i1], pad_width, **pad_kws[padding])
+        for k_ in range(0, n1, self.hop):
+            yield x1[..., k_:k_ + self.m_num]
+
+    def stft(self, x: np.ndarray, p0: int | None = None,
+             p1: int | None = None, *, k_offset: int = 0,
+             padding: PAD_TYPE = 'zeros', axis: int = -1) \
+            -> np.ndarray:
+        """Perform the short-time Fourier transform.
+
+        A two-dimensional matrix with ``p1-p0`` columns is calculated.
+        The `f_pts` rows represent value at the frequencies `f`. The q-th
+        column of the windowed FFT with the window `win` is centered at t[q].
+        The columns represent the values at the frequencies `f`.
+
+        Parameters
+        ----------
+        x
+            The input signal as real or complex valued array. For complex values, the
+            property `fft_mode` must be set to 'twosided' or 'centered'.
+        p0
+            The first element of the range of slices to calculate. If ``None``
+            then it is set to :attr:`p_min`, which is the smallest possible
+            slice.
+        p1
+            The end of the array. If ``None`` then `p_max(n)` is used.
+        k_offset
+            Index of first sample (t = 0) in `x`.
+        padding
+            Kind of values which are added, when the sliding window sticks out
+            on either the lower or upper end of the input `x`. Zeros are added
+            if the default 'zeros' is set. For 'edge' either the first or the
+            last value of `x` is used. 'even' pads by reflecting the
+            signal on the first or last sample and 'odd' additionally
+            multiplies it with -1.
+        axis
+            The axis of `x` over which to compute the STFT.
+            If not given, the last axis is used.
+
+        Returns
+        -------
+        S
+            A complex array is returned with the dimension always being larger
+            by one than of `x`. The last axis always represent the time slices
+            of the STFT. `axis` defines the frequency axis (default second to
+            last). E.g., for a one-dimensional `x`, a complex 2d array is
+            returned, with axis 0 representing frequency and axis 1 the time
+            slices.
+
+        See Also
+        --------
+        delta_f: Width of the frequency bins of the STFT.
+        delta_t: Time increment of STFT
+        f: Frequencies values of the STFT.
+        invertible: Check if STFT is invertible.
+        :meth:`~ShortTimeFFT.istft`: Inverse short-time Fourier transform.
+        p_range: Determine and validate slice index range.
+        stft_detrend: STFT with detrended segments.
+        t: Times of STFT for an input signal with `n` samples.
+        :class:`scipy.signal.ShortTimeFFT`: Class this method belongs to.
+        """
+        return self.stft_detrend(x, None, p0, p1, k_offset=k_offset,
+                                 padding=padding, axis=axis)
+
+    def stft_detrend(self, x: np.ndarray,
+                     detr: Callable[[np.ndarray], np.ndarray] | Literal['linear', 'constant'] | None,  # noqa: E501
+                     p0: int | None = None, p1: int | None = None, *,
+                     k_offset: int = 0, padding: PAD_TYPE = 'zeros',
+                     axis: int = -1) \
+            -> np.ndarray:
+        """Short-time Fourier transform with a trend being subtracted from each
+        segment beforehand.
+
+        If `detr` is set to 'constant', the mean is subtracted, if set to
+        "linear", the linear trend is removed. This is achieved by calling
+        :func:`scipy.signal.detrend`. If `detr` is a function, `detr` is
+        applied to each segment.
+        All other parameters have the same meaning as in `~ShortTimeFFT.stft`.
+
+        Note that due to the detrending, the original signal cannot be
+        reconstructed by the `~ShortTimeFFT.istft`.
+
+        See Also
+        --------
+        invertible: Check if STFT is invertible.
+        :meth:`~ShortTimeFFT.istft`: Inverse short-time Fourier transform.
+        :meth:`~ShortTimeFFT.stft`: Short-time Fourier transform
+                                   (without detrending).
+        :class:`scipy.signal.ShortTimeFFT`: Class this method belongs to.
+        """
+        if self.onesided_fft and np.iscomplexobj(x):
+            raise ValueError(f"Complex-valued `x` not allowed for {self.fft_mode=}'! "
+                             "Set property `fft_mode` to 'twosided' or 'centered'.")
+        if isinstance(detr, str):
+            detr = partial(detrend, type=detr)
+        elif not (detr is None or callable(detr)):
+            raise ValueError(f"Parameter {detr=} is not a str, function or " +
+                             "None!")
+        n = x.shape[axis]
+        if not (n >= (m2p := self.m_num-self.m_num_mid)):
+            e_str = f'{len(x)=}' if x.ndim == 1 else f'of {axis=} of {x.shape}'
+            raise ValueError(f"{e_str} must be >= ceil(m_num/2) = {m2p}!")
+
+        if x.ndim > 1:  # motivated by the NumPy broadcasting mechanisms:
+            x = np.moveaxis(x, axis, -1)
+        # determine slice index range:
+        p0, p1 = self.p_range(n, p0, p1)
+        S_shape_1d = (self.f_pts, p1 - p0)
+        S_shape = x.shape[:-1] + S_shape_1d if x.ndim > 1 else S_shape_1d
+        S = np.zeros(S_shape, dtype=complex)
+        for p_, x_ in enumerate(self._x_slices(x, k_offset, p0, p1, padding)):
+            if detr is not None:
+                x_ = detr(x_)
+            S[..., :, p_] = self._fft_func(x_ * self.win.conj())
+        if x.ndim > 1:
+            return np.moveaxis(S, -2, axis if axis >= 0 else axis-1)
+        return S
+
+    def spectrogram(self, x: np.ndarray, y: np.ndarray | None = None,
+                    detr: Callable[[np.ndarray], np.ndarray] | Literal['linear', 'constant'] | None = None,  # noqa: E501
+                    *,
+                    p0: int | None = None, p1: int | None = None,
+                    k_offset: int = 0, padding: PAD_TYPE = 'zeros',
+                    axis: int = -1) \
+            -> np.ndarray:
+        r"""Calculate spectrogram or cross-spectrogram.
+
+        The spectrogram is the absolute square of the STFT, i.e., it is
+        ``abs(S[q,p])**2`` for given ``S[q,p]``  and thus is always
+        non-negative.
+        For two STFTs ``Sx[q,p], Sy[q,p]``, the cross-spectrogram is defined
+        as ``Sx[q,p] * np.conj(Sy[q,p])`` and is complex-valued.
+        This is a convenience function for calling `~ShortTimeFFT.stft` /
+        `stft_detrend`, hence all parameters are discussed there. If `y` is not
+        ``None`` it needs to have the same shape as `x`.
+
+        Examples
+        --------
+        The following example shows the spectrogram of a square wave with
+        varying frequency :math:`f_i(t)` (marked by a green dashed line in the
+        plot) sampled with 20 Hz:
+
+        >>> import matplotlib.pyplot as plt
+        >>> import numpy as np
+        >>> from scipy.signal import square, ShortTimeFFT
+        >>> from scipy.signal.windows import gaussian
+        ...
+        >>> T_x, N = 1 / 20, 1000  # 20 Hz sampling rate for 50 s signal
+        >>> t_x = np.arange(N) * T_x  # time indexes for signal
+        >>> f_i = 5e-3*(t_x - t_x[N // 3])**2 + 1  # varying frequency
+        >>> x = square(2*np.pi*np.cumsum(f_i)*T_x)  # the signal
+
+        The utilized Gaussian window is 50 samples or 2.5 s long. The
+        parameter ``mfft=800`` (oversampling factor 16) and the `hop` interval
+        of 2 in `ShortTimeFFT` was chosen to produce a sufficient number of
+        points:
+
+        >>> g_std = 12  # standard deviation for Gaussian window in samples
+        >>> win = gaussian(50, std=g_std, sym=True)  # symmetric Gaussian wind.
+        >>> SFT = ShortTimeFFT(win, hop=2, fs=1/T_x, mfft=800, scale_to='psd')
+        >>> Sx2 = SFT.spectrogram(x)  # calculate absolute square of STFT
+
+        The plot's colormap is logarithmically scaled as the power spectral
+        density is in dB. The time extent of the signal `x` is marked by
+        vertical dashed lines and the shaded areas mark the presence of border
+        effects:
+
+        >>> fig1, ax1 = plt.subplots(figsize=(6., 4.))  # enlarge plot a bit
+        >>> t_lo, t_hi = SFT.extent(N)[:2]  # time range of plot
+        >>> ax1.set_title(rf"Spectrogram ({SFT.m_num*SFT.T:g}$\,s$ Gaussian " +
+        ...               rf"window, $\sigma_t={g_std*SFT.T:g}\,$s)")
+        >>> ax1.set(xlabel=f"Time $t$ in seconds ({SFT.p_num(N)} slices, " +
+        ...                rf"$\Delta t = {SFT.delta_t:g}\,$s)",
+        ...         ylabel=f"Freq. $f$ in Hz ({SFT.f_pts} bins, " +
+        ...                rf"$\Delta f = {SFT.delta_f:g}\,$Hz)",
+        ...         xlim=(t_lo, t_hi))
+        >>> Sx_dB = 10 * np.log10(np.fmax(Sx2, 1e-4))  # limit range to -40 dB
+        >>> im1 = ax1.imshow(Sx_dB, origin='lower', aspect='auto',
+        ...                  extent=SFT.extent(N), cmap='magma')
+        >>> ax1.plot(t_x, f_i, 'g--', alpha=.5, label='$f_i(t)$')
+        >>> fig1.colorbar(im1, label='Power Spectral Density ' +
+        ...                          r"$20\,\log_{10}|S_x(t, f)|$ in dB")
+        ...
+        >>> # Shade areas where window slices stick out to the side:
+        >>> for t0_, t1_ in [(t_lo, SFT.lower_border_end[0] * SFT.T),
+        ...                  (SFT.upper_border_begin(N)[0] * SFT.T, t_hi)]:
+        ...     ax1.axvspan(t0_, t1_, color='w', linewidth=0, alpha=.3)
+        >>> for t_ in [0, N * SFT.T]:  # mark signal borders with vertical line
+        ...     ax1.axvline(t_, color='c', linestyle='--', alpha=0.5)
+        >>> ax1.legend()
+        >>> fig1.tight_layout()
+        >>> plt.show()
+
+        The logarithmic scaling reveals the odd harmonics of the square wave,
+        which are reflected at the Nyquist frequency of 10 Hz. This aliasing
+        is also the main source of the noise artifacts in the plot.
+
+
+        See Also
+        --------
+        :meth:`~ShortTimeFFT.stft`: Perform the short-time Fourier transform.
+        stft_detrend: STFT with a trend subtracted from each segment.
+        :class:`scipy.signal.ShortTimeFFT`: Class this method belongs to.
+        """
+        Sx = self.stft_detrend(x, detr, p0, p1, k_offset=k_offset,
+                               padding=padding, axis=axis)
+        if y is None or y is x:  # do spectrogram:
+            return Sx.real**2 + Sx.imag**2
+        # Cross-spectrogram:
+        Sy = self.stft_detrend(y, detr, p0, p1, k_offset=k_offset,
+                               padding=padding, axis=axis)
+        return Sx * Sy.conj()
+
+    @property
+    def dual_win(self) -> np.ndarray:
+        """Canonical dual window.
+
+        A STFT can be interpreted as the input signal being expressed as a
+        weighted sum of modulated and time-shifted dual windows. Note that for
+        a given window there exist many dual windows. The canonical window is
+        the one with the minimal energy (i.e., :math:`L_2` norm).
+
+        `dual_win` has same length as `win`, namely `m_num` samples.
+
+        If the dual window cannot be calculated a ``ValueError`` is raised.
+        This attribute is read only and calculated lazily.
+
+        See Also
+        --------
+        dual_win: Canonical dual window.
+        m_num: Number of samples in window `win`.
+        win: Window function as real- or complex-valued 1d array.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        if self._dual_win is None:
+            self._dual_win = _calc_dual_canonical_window(self.win, self.hop)
+        return self._dual_win
+
+    @property
+    def invertible(self) -> bool:
+        """Check if STFT is invertible.
+
+        This is achieved by trying to calculate the canonical dual window.
+
+        See Also
+        --------
+        :meth:`~ShortTimeFFT.istft`: Inverse short-time Fourier transform.
+        m_num: Number of samples in window `win` and `dual_win`.
+        dual_win: Canonical dual window.
+        win: Window for STFT.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        try:
+            return len(self.dual_win) > 0  # call self.dual_win()
+        except ValueError:
+            return False
+
+    def istft(self, S: np.ndarray, k0: int = 0, k1: int | None = None, *,
+              f_axis: int = -2, t_axis: int = -1) \
+            -> np.ndarray:
+        """Inverse short-time Fourier transform.
+
+        It returns an array of dimension ``S.ndim - 1``  which is real
+        if `onesided_fft` is set, else complex. If the STFT is not
+        `invertible`, or the parameters are out of bounds  a ``ValueError`` is
+        raised.
+
+        Parameters
+        ----------
+        S
+            A complex valued array where `f_axis` denotes the frequency
+            values and the `t-axis` dimension the temporal values of the
+            STFT values.
+        k0, k1
+            The start and the end index of the reconstructed signal. The
+            default (``k0 = 0``, ``k1 = None``) assumes that the maximum length
+            signal should be reconstructed.
+        f_axis, t_axis
+            The axes in `S` denoting the frequency and the time dimension.
+
+        Notes
+        -----
+        It is required that `S` has `f_pts` entries along the `f_axis`. For
+        the `t_axis` it is assumed that the first entry corresponds to
+        `p_min` * `delta_t` (being <= 0). The length of `t_axis` needs to be
+        compatible with `k1`. I.e., ``S.shape[t_axis] >= self.p_max(k1)`` must
+        hold, if `k1` is not ``None``. Else `k1` is set to `k_max` with::
+
+            q_max = S.shape[t_range] + self.p_min
+            k_max = (q_max - 1) * self.hop + self.m_num - self.m_num_mid
+
+        The :ref:`tutorial_stft` section of the :ref:`user_guide` discussed the
+        slicing behavior by means of an example.
+
+        See Also
+        --------
+        invertible: Check if STFT is invertible.
+        :meth:`~ShortTimeFFT.stft`: Perform Short-time Fourier transform.
+        :class:`scipy.signal.ShortTimeFFT`: Class this method belongs to.
+        """
+        if f_axis == t_axis:
+            raise ValueError(f"{f_axis=} may not be equal to {t_axis=}!")
+        if S.shape[f_axis] != self.f_pts:
+            raise ValueError(f"{S.shape[f_axis]=} must be equal to " +
+                             f"{self.f_pts=} ({S.shape=})!")
+        n_min = self.m_num-self.m_num_mid  # minimum signal length
+        if not (S.shape[t_axis] >= (q_num := self.p_num(n_min))):
+            raise ValueError(f"{S.shape[t_axis]=} needs to have at least " +
+                             f"{q_num} slices ({S.shape=})!")
+        if t_axis != S.ndim - 1 or f_axis != S.ndim - 2:
+            t_axis = S.ndim + t_axis if t_axis < 0 else t_axis
+            f_axis = S.ndim + f_axis if f_axis < 0 else f_axis
+            S = np.moveaxis(S, (f_axis, t_axis), (-2, -1))
+
+        q_max = S.shape[-1] + self.p_min
+        k_max = (q_max - 1) * self.hop + self.m_num - self.m_num_mid
+
+        k1 = k_max if k1 is None else k1
+        if not (self.k_min <= k0 < k1 <= k_max):
+            raise ValueError(f"({self.k_min=}) <= ({k0=}) < ({k1=}) <= " +
+                             f"({k_max=}) is false!")
+        if not (num_pts := k1 - k0) >= n_min:
+            raise ValueError(f"({k1=}) - ({k0=}) = {num_pts} has to be at " +
+                             f"least the half the window length {n_min}!")
+
+        q0 = (k0 // self.hop + self.p_min if k0 >= 0 else  # p_min always <= 0
+              k0 // self.hop)
+        q1 = min(self.p_max(k1), q_max)
+        k_q0, k_q1 = self.nearest_k_p(k0), self.nearest_k_p(k1, left=False)
+        n_pts = k_q1 - k_q0 + self.m_num - self.m_num_mid
+        x = np.zeros(S.shape[:-2] + (n_pts,),
+                     dtype=float if self.onesided_fft else complex)
+        for q_ in range(q0, q1):
+            xs = self._ifft_func(S[..., :, q_ - self.p_min]) * self.dual_win
+            i0 = q_ * self.hop - self.m_num_mid
+            i1 = min(i0 + self.m_num, n_pts+k0)
+            j0, j1 = 0, i1 - i0
+            if i0 < k0:  # xs sticks out to the left on x:
+                j0 += k0 - i0
+                i0 = k0
+            x[..., i0-k0:i1-k0] += xs[..., j0:j1]
+        x = x[..., :k1-k0]
+        if x.ndim > 1:
+            x = np.moveaxis(x, -1, f_axis if f_axis < x.ndim else t_axis)
+        return x
+
+    @property
+    def fac_magnitude(self) -> float:
+        """Factor to multiply the STFT values by to scale each frequency slice
+        to a magnitude spectrum.
+
+        It is 1 if attribute ``scaling == 'magnitude'``.
+        The window can be scaled to a magnitude spectrum by using the method
+        `scale_to`.
+
+        See Also
+        --------
+        fac_psd: Scaling factor for to a power spectral density spectrum.
+        scale_to: Scale window to obtain 'magnitude' or 'psd' scaling.
+        scaling: Normalization applied to the window function.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        if self.scaling == 'magnitude':
+            return 1
+        if self._fac_mag is None:
+            self._fac_mag = 1 / abs(sum(self.win))
+        return self._fac_mag
+
+    @property
+    def fac_psd(self) -> float:
+        """Factor to multiply the STFT values by to scale each frequency slice
+        to a power spectral density (PSD).
+
+        It is 1 if attribute ``scaling == 'psd'``.
+        The window can be scaled to a psd spectrum by using the method
+        `scale_to`.
+
+        See Also
+        --------
+        fac_magnitude: Scaling factor for to a magnitude spectrum.
+        scale_to: Scale window to obtain 'magnitude' or 'psd' scaling.
+        scaling: Normalization applied to the window function.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        if self.scaling == 'psd':
+            return 1
+        if self._fac_psd is None:
+            self._fac_psd = 1 / np.sqrt(
+                sum(self.win.real**2+self.win.imag**2) / self.T)
+        return self._fac_psd
+
+    @property
+    def m_num(self) -> int:
+        """Number of samples in window `win`.
+
+        Note that the FFT can be oversampled by zero-padding. This is achieved
+        by setting the `mfft` property.
+
+        See Also
+        --------
+        m_num_mid: Center index of window `win`.
+        mfft: Length of input for the FFT used - may be larger than `m_num`.
+        hop: Time increment in signal samples for sliding window.
+        win: Window function as real- or complex-valued 1d array.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return len(self.win)
+
+    @property
+    def m_num_mid(self) -> int:
+        """Center index of window `win`.
+
+        For odd `m_num`, ``(m_num - 1) / 2`` is returned and
+        for even `m_num` (per definition) ``m_num / 2`` is returned.
+
+        See Also
+        --------
+        m_num: Number of samples in window `win`.
+        mfft: Length of input for the FFT used - may be larger than `m_num`.
+        hop: ime increment in signal samples for sliding window.
+        win: Window function as real- or complex-valued 1d array.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self.m_num // 2
+
+    @cache
+    def _pre_padding(self) -> tuple[int, int]:
+        """Smallest signal index and slice index due to padding.
+
+         Since, per convention, for time t=0, n,q is zero, the returned values
+         are negative or zero.
+         """
+        w2 = self.win.real**2 + self.win.imag**2
+        # move window to the left until the overlap with t >= 0 vanishes:
+        n0 = -self.m_num_mid
+        for q_, n_ in enumerate(range(n0, n0-self.m_num-1, -self.hop)):
+            n_next = n_ - self.hop
+            if n_next + self.m_num <= 0 or all(w2[n_next:] == 0):
+                return n_, -q_
+        raise RuntimeError("This is code line should not have been reached!")
+        # If this case is reached, it probably means the first slice should be
+        # returned, i.e.: return n0, 0
+
+    @property
+    def k_min(self) -> int:
+        """The smallest possible signal index of the STFT.
+
+        `k_min` is the index of the left-most non-zero value of the lowest
+        slice `p_min`. Since the zeroth slice is centered over the zeroth
+        sample of the input signal, `k_min` is never positive.
+        A detailed example is provided in the :ref:`tutorial_stft_sliding_win`
+        section of the :ref:`user_guide`.
+
+        See Also
+        --------
+        k_max: First sample index after signal end not touched by a time slice.
+        lower_border_end: Where pre-padding effects end.
+        p_min: The smallest possible slice index.
+        p_max: Index of first non-overlapping upper time slice.
+        p_num: Number of time slices, i.e., `p_max` - `p_min`.
+        p_range: Determine and validate slice index range.
+        upper_border_begin: Where post-padding effects start.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self._pre_padding()[0]
+
+    @property
+    def p_min(self) -> int:
+        """The smallest possible slice index.
+
+        `p_min` is the index of the left-most slice, where the window still
+        sticks into the signal, i.e., has non-zero part for t >= 0.
+        `k_min` is the smallest index where the window function of the slice
+        `p_min` is non-zero.
+
+        Since, per convention the zeroth slice is centered at t=0,
+        `p_min` <= 0 always holds.
+        A detailed example is provided in the :ref:`tutorial_stft_sliding_win`
+        section of the :ref:`user_guide`.
+
+        See Also
+        --------
+        k_min: The smallest possible signal index.
+        k_max: First sample index after signal end not touched by a time slice.
+        p_max: Index of first non-overlapping upper time slice.
+        p_num: Number of time slices, i.e., `p_max` - `p_min`.
+        p_range: Determine and validate slice index range.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self._pre_padding()[1]
+
+    @lru_cache(maxsize=256)
+    def _post_padding(self, n: int) -> tuple[int, int]:
+        """Largest signal index and slice index due to padding."""
+        w2 = self.win.real**2 + self.win.imag**2
+        # move window to the right until the overlap for t < t[n] vanishes:
+        q1 = n // self.hop   # last slice index with t[p1] <= t[n]
+        k1 = q1 * self.hop - self.m_num_mid
+        for q_, k_ in enumerate(range(k1, n+self.m_num, self.hop), start=q1):
+            n_next = k_ + self.hop
+            if n_next >= n or all(w2[:n-n_next] == 0):
+                return k_ + self.m_num, q_ + 1
+        raise RuntimeError("This is code line should not have been reached!")
+        # If this case is reached, it probably means the last slice should be
+        # returned, i.e.: return k1 + self.m_num - self.m_num_mid, q1 + 1
+
+    def k_max(self, n: int) -> int:
+        """First sample index after signal end not touched by a time slice.
+
+        `k_max` - 1 is the largest sample index of the slice `p_max` for a
+        given input signal of `n` samples.
+        A detailed example is provided in the :ref:`tutorial_stft_sliding_win`
+        section of the :ref:`user_guide`.
+
+        See Also
+        --------
+        k_min: The smallest possible signal index.
+        p_min: The smallest possible slice index.
+        p_max: Index of first non-overlapping upper time slice.
+        p_num: Number of time slices, i.e., `p_max` - `p_min`.
+        p_range: Determine and validate slice index range.
+        ShortTimeFFT: Class this method belongs to.
+        """
+        return self._post_padding(n)[0]
+
+    def p_max(self, n: int) -> int:
+        """Index of first non-overlapping upper time slice for `n` sample
+        input.
+
+        Note that center point t[p_max] = (p_max(n)-1) * `delta_t` is typically
+        larger than last time index t[n-1] == (`n`-1) * `T`. The upper border
+        of samples indexes covered by the window slices is given by `k_max`.
+        Furthermore, `p_max` does not denote the number of slices `p_num` since
+        `p_min` is typically less than zero.
+        A detailed example is provided in the :ref:`tutorial_stft_sliding_win`
+        section of the :ref:`user_guide`.
+
+        See Also
+        --------
+        k_min: The smallest possible signal index.
+        k_max: First sample index after signal end not touched by a time slice.
+        p_min: The smallest possible slice index.
+        p_num: Number of time slices, i.e., `p_max` - `p_min`.
+        p_range: Determine and validate slice index range.
+        ShortTimeFFT: Class this method belongs to.
+        """
+        return self._post_padding(n)[1]
+
+    def p_num(self, n: int) -> int:
+        """Number of time slices for an input signal with `n` samples.
+
+        It is given by `p_num` = `p_max` - `p_min` with `p_min` typically
+        being negative.
+        A detailed example is provided in the :ref:`tutorial_stft_sliding_win`
+        section of the :ref:`user_guide`.
+
+        See Also
+        --------
+        k_min: The smallest possible signal index.
+        k_max: First sample index after signal end not touched by a time slice.
+        lower_border_end: Where pre-padding effects end.
+        p_min: The smallest possible slice index.
+        p_max: Index of first non-overlapping upper time slice.
+        p_range: Determine and validate slice index range.
+        upper_border_begin: Where post-padding effects start.
+        ShortTimeFFT: Class this method belongs to.
+        """
+        return self.p_max(n) - self.p_min
+
+    @property
+    def lower_border_end(self) -> tuple[int, int]:
+        """First signal index and first slice index unaffected by pre-padding.
+
+        Describes the point where the window does not stick out to the left
+        of the signal domain.
+        A detailed example is provided in the :ref:`tutorial_stft_sliding_win`
+        section of the :ref:`user_guide`.
+
+        See Also
+        --------
+        k_min: The smallest possible signal index.
+        k_max: First sample index after signal end not touched by a time slice.
+        lower_border_end: Where pre-padding effects end.
+        p_min: The smallest possible slice index.
+        p_max: Index of first non-overlapping upper time slice.
+        p_num: Number of time slices, i.e., `p_max` - `p_min`.
+        p_range: Determine and validate slice index range.
+        upper_border_begin: Where post-padding effects start.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        # not using @cache decorator due to MyPy limitations
+        if self._lower_border_end is not None:
+            return self._lower_border_end
+
+        # first non-zero element in self.win:
+        m0 = np.flatnonzero(self.win.real**2 + self.win.imag**2)[0]
+
+        # move window to the right until does not stick out to the left:
+        k0 = -self.m_num_mid + m0
+        for q_, k_ in enumerate(range(k0, self.hop + 1, self.hop)):
+            if k_ + self.hop >= 0:  # next entry does not stick out anymore
+                self._lower_border_end = (k_ + self.m_num, q_ + 1)
+                return self._lower_border_end
+        self._lower_border_end = (0, max(self.p_min, 0))  # ends at first slice
+        return self._lower_border_end
+
+    @lru_cache(maxsize=256)
+    def upper_border_begin(self, n: int) -> tuple[int, int]:
+        """First signal index and first slice index affected by post-padding.
+
+        Describes the point where the window does begin stick out to the right
+        of the signal domain.
+        A detailed example is given :ref:`tutorial_stft_sliding_win` section
+        of the :ref:`user_guide`.
+
+        See Also
+        --------
+        k_min: The smallest possible signal index.
+        k_max: First sample index after signal end not touched by a time slice.
+        lower_border_end: Where pre-padding effects end.
+        p_min: The smallest possible slice index.
+        p_max: Index of first non-overlapping upper time slice.
+        p_num: Number of time slices, i.e., `p_max` - `p_min`.
+        p_range: Determine and validate slice index range.
+        ShortTimeFFT: Class this method belongs to.
+        """
+        w2 = self.win.real**2 + self.win.imag**2
+        q2 = n // self.hop + 1  # first t[q] >= t[n]
+        q1 = max((n-self.m_num) // self.hop - 1, -1)
+        # move window left until does not stick out to the right:
+        for q_ in range(q2, q1, -1):
+            k_ = q_ * self.hop + (self.m_num - self.m_num_mid)
+            if k_ < n or all(w2[n-k_:] == 0):
+                return (q_ + 1) * self.hop - self.m_num_mid, q_ + 1
+        return 0, 0  # border starts at first slice
+
+    @property
+    def delta_t(self) -> float:
+        """Time increment of STFT.
+
+        The time increment `delta_t` = `T` * `hop` represents the sample
+        increment `hop` converted to time based on the sampling interval `T`.
+
+        See Also
+        --------
+        delta_f: Width of the frequency bins of the STFT.
+        hop: Hop size in signal samples for sliding window.
+        t: Times of STFT for an input signal with `n` samples.
+        T: Sampling interval of input signal and window `win`.
+        ShortTimeFFT: Class this property belongs to
+        """
+        return self.T * self.hop
+
+    def p_range(self, n: int, p0: int | None = None,
+                p1: int | None = None) -> tuple[int, int]:
+        """Determine and validate slice index range.
+
+        Parameters
+        ----------
+        n : int
+            Number of samples of input signal, assuming t[0] = 0.
+        p0 : int | None
+            First slice index. If 0 then the first slice is centered at t = 0.
+            If ``None`` then `p_min` is used. Note that p0 may be < 0 if
+            slices are left of t = 0.
+        p1 : int | None
+            End of interval (last value is p1-1).
+            If ``None`` then `p_max(n)` is used.
+
+
+        Returns
+        -------
+        p0_ : int
+            The fist slice index
+        p1_ : int
+            End of interval (last value is p1-1).
+
+        Notes
+        -----
+        A ``ValueError`` is raised if ``p_min <= p0 < p1 <= p_max(n)`` does not
+        hold.
+
+        See Also
+        --------
+        k_min: The smallest possible signal index.
+        k_max: First sample index after signal end not touched by a time slice.
+        lower_border_end: Where pre-padding effects end.
+        p_min: The smallest possible slice index.
+        p_max: Index of first non-overlapping upper time slice.
+        p_num: Number of time slices, i.e., `p_max` - `p_min`.
+        upper_border_begin: Where post-padding effects start.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        p_max = self.p_max(n)  # shorthand
+        p0_ = self.p_min if p0 is None else p0
+        p1_ = p_max if p1 is None else p1
+        if not (self.p_min <= p0_ < p1_ <= p_max):
+            raise ValueError(f"Invalid Parameter {p0=}, {p1=}, i.e., " +
+                             f"{self.p_min=} <= p0 < p1 <= {p_max=} " +
+                             f"does not hold for signal length {n=}!")
+        return p0_, p1_
+
+    @lru_cache(maxsize=1)
+    def t(self, n: int, p0: int | None = None, p1: int | None = None,
+          k_offset: int = 0) -> np.ndarray:
+        """Times of STFT for an input signal with `n` samples.
+
+        Returns a 1d array with times of the `~ShortTimeFFT.stft` values with
+        the same  parametrization. Note that the slices are
+        ``delta_t = hop * T`` time units apart.
+
+         Parameters
+        ----------
+        n
+            Number of sample of the input signal.
+        p0
+            The first element of the range of slices to calculate. If ``None``
+            then it is set to :attr:`p_min`, which is the smallest possible
+            slice.
+        p1
+            The end of the array. If ``None`` then `p_max(n)` is used.
+        k_offset
+            Index of first sample (t = 0) in `x`.
+
+
+        See Also
+        --------
+        delta_t: Time increment of STFT (``hop*T``)
+        hop: Time increment in signal samples for sliding window.
+        nearest_k_p: Nearest sample index k_p for which t[k_p] == t[p] holds.
+        T: Sampling interval of input signal and of the window (``1/fs``).
+        fs: Sampling frequency (being ``1/T``)
+        ShortTimeFFT: Class this method belongs to.
+        """
+        p0, p1 = self.p_range(n, p0, p1)
+        return np.arange(p0, p1) * self.delta_t + k_offset * self.T
+
+    def nearest_k_p(self, k: int, left: bool = True) -> int:
+        """Return nearest sample index k_p for which t[k_p] == t[p] holds.
+
+        The nearest next smaller time sample p (where t[p] is the center
+        position of the window of the p-th slice) is p_k = k // `hop`.
+        If `hop` is a divisor of `k` than `k` is returned.
+        If `left` is set than p_k * `hop` is returned else (p_k+1) * `hop`.
+
+        This method can be used to slice an input signal into chunks for
+        calculating the STFT and iSTFT incrementally.
+
+        See Also
+        --------
+        delta_t: Time increment of STFT (``hop*T``)
+        hop: Time increment in signal samples for sliding window.
+        T: Sampling interval of input signal and of the window (``1/fs``).
+        fs: Sampling frequency (being ``1/T``)
+        t: Times of STFT for an input signal with `n` samples.
+        ShortTimeFFT: Class this method belongs to.
+        """
+        p_q, remainder = divmod(k, self.hop)
+        if remainder == 0:
+            return k
+        return p_q * self.hop if left else (p_q + 1) * self.hop
+
+    @property
+    def delta_f(self) -> float:
+        """Width of the frequency bins of the STFT.
+
+        Return the frequency interval `delta_f` = 1 / (`mfft` * `T`).
+
+        See Also
+        --------
+        delta_t: Time increment of STFT.
+        f_pts: Number of points along the frequency axis.
+        f: Frequencies values of the STFT.
+        mfft: Length of the input for FFT used.
+        T: Sampling interval.
+        t: Times of STFT for an input signal with `n` samples.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return 1 / (self.mfft * self.T)
+
+    @property
+    def f_pts(self) -> int:
+        """Number of points along the frequency axis.
+
+        See Also
+        --------
+        delta_f: Width of the frequency bins of the STFT.
+        f: Frequencies values of the STFT.
+        mfft: Length of the input for FFT used.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self.mfft // 2 + 1 if self.onesided_fft else self.mfft
+
+    @property
+    def onesided_fft(self) -> bool:
+        """Return True if a one-sided FFT is used.
+
+        Returns ``True`` if `fft_mode` is either 'onesided' or 'onesided2X'.
+
+        See Also
+        --------
+        fft_mode: Utilized FFT ('twosided', 'centered', 'onesided' or
+                 'onesided2X')
+        ShortTimeFFT: Class this property belongs to.
+        """
+        return self.fft_mode in {'onesided', 'onesided2X'}
+
+    @property
+    def f(self) -> np.ndarray:
+        """Frequencies values of the STFT.
+
+        A 1d array of length `f_pts` with `delta_f` spaced entries is returned.
+
+        See Also
+        --------
+        delta_f: Width of the frequency bins of the STFT.
+        f_pts: Number of points along the frequency axis.
+        mfft: Length of the input for FFT used.
+        ShortTimeFFT: Class this property belongs to.
+        """
+        if self.fft_mode in {'onesided', 'onesided2X'}:
+            return fft_lib.rfftfreq(self.mfft, self.T)
+        elif self.fft_mode == 'twosided':
+            return fft_lib.fftfreq(self.mfft, self.T)
+        elif self.fft_mode == 'centered':
+            return fft_lib.fftshift(fft_lib.fftfreq(self.mfft, self.T))
+        # This should never happen but makes the Linters happy:
+        fft_modes = get_args(FFT_MODE_TYPE)
+        raise RuntimeError(f"{self.fft_mode=} not in {fft_modes}!")
+
+    def _fft_func(self, x: np.ndarray) -> np.ndarray:
+        """FFT based on the `fft_mode`, `mfft`, `scaling` and `phase_shift`
+        attributes.
+
+        For multidimensional arrays the transformation is carried out on the
+        last axis.
+        """
+        if self.phase_shift is not None:
+            if x.shape[-1] < self.mfft:  # zero pad if needed
+                z_shape = list(x.shape)
+                z_shape[-1] = self.mfft - x.shape[-1]
+                x = np.hstack((x, np.zeros(z_shape, dtype=x.dtype)))
+            p_s = (self.phase_shift + self.m_num_mid) % self.m_num
+            x = np.roll(x, -p_s, axis=-1)
+
+        if self.fft_mode == 'twosided':
+            return fft_lib.fft(x, n=self.mfft, axis=-1)
+        if self.fft_mode == 'centered':
+            return fft_lib.fftshift(fft_lib.fft(x, self.mfft, axis=-1), axes=-1)
+        if self.fft_mode == 'onesided':
+            return fft_lib.rfft(x, n=self.mfft, axis=-1)
+        if self.fft_mode == 'onesided2X':
+            X = fft_lib.rfft(x, n=self.mfft, axis=-1)
+            # Either squared magnitude (psd) or magnitude is doubled:
+            fac = np.sqrt(2) if self.scaling == 'psd' else 2
+            # For even input length, the last entry is unpaired:
+            X[..., 1: -1 if self.mfft % 2 == 0 else None] *= fac
+            return X
+        # This should never happen but makes the Linter happy:
+        fft_modes = get_args(FFT_MODE_TYPE)
+        raise RuntimeError(f"{self.fft_mode=} not in {fft_modes}!")
+
+    def _ifft_func(self, X: np.ndarray) -> np.ndarray:
+        """Inverse to `_fft_func`.
+
+        Returned is an array of length `m_num`. If the FFT is `onesided`
+        then a float array is returned else a complex array is returned.
+        For multidimensional arrays the transformation is carried out on the
+        last axis.
+        """
+        if self.fft_mode == 'twosided':
+            x = fft_lib.ifft(X, n=self.mfft, axis=-1)
+        elif self.fft_mode == 'centered':
+            x = fft_lib.ifft(fft_lib.ifftshift(X, axes=-1), n=self.mfft, axis=-1)
+        elif self.fft_mode == 'onesided':
+            x = fft_lib.irfft(X, n=self.mfft, axis=-1)
+        elif self.fft_mode == 'onesided2X':
+            Xc = X.copy()  # we do not want to modify function parameters
+            fac = np.sqrt(2) if self.scaling == 'psd' else 2
+            # For even length X the last value is not paired with a negative
+            # value on the two-sided FFT:
+            q1 = -1 if self.mfft % 2 == 0 else None
+            Xc[..., 1:q1] /= fac
+            x = fft_lib.irfft(Xc, n=self.mfft, axis=-1)
+        else:  # This should never happen but makes the Linter happy:
+            error_str = f"{self.fft_mode=} not in {get_args(FFT_MODE_TYPE)}!"
+            raise RuntimeError(error_str)
+
+        if self.phase_shift is None:
+            return x[..., :self.m_num]
+        p_s = (self.phase_shift + self.m_num_mid) % self.m_num
+        return np.roll(x, p_s, axis=-1)[..., :self.m_num]
+
+    def extent(self, n: int, axes_seq: Literal['tf', 'ft'] = 'tf',
+               center_bins: bool = False) -> tuple[float, float, float, float]:
+        """Return minimum and maximum values time-frequency values.
+
+        A tuple with four floats  ``(t0, t1, f0, f1)`` for 'tf' and
+        ``(f0, f1, t0, t1)`` for 'ft' is returned describing the corners
+        of the time-frequency domain of the `~ShortTimeFFT.stft`.
+        That tuple can be passed to `matplotlib.pyplot.imshow` as a parameter
+        with the same name.
+
+        Parameters
+        ----------
+        n : int
+            Number of samples in input signal.
+        axes_seq : {'tf', 'ft'}
+            Return time extent first and then frequency extent or vice-versa.
+        center_bins: bool
+            If set (default ``False``), the values of the time slots and
+            frequency bins are moved from the side the middle. This is useful,
+            when plotting the `~ShortTimeFFT.stft` values as step functions,
+            i.e., with no interpolation.
+
+        See Also
+        --------
+        :func:`matplotlib.pyplot.imshow`: Display data as an image.
+        :class:`scipy.signal.ShortTimeFFT`: Class this method belongs to.
+
+        Examples
+        --------
+        The following two plots illustrate the effect of the parameter `center_bins`:
+        The grid lines represent the three time and the four frequency values of the
+        STFT.
+        The left plot, where ``(t0, t1, f0, f1) = (0, 3, 0, 4)`` is passed as parameter
+        ``extent`` to `~matplotlib.pyplot.imshow`, shows the standard behavior of the
+        time and frequency values being at the lower edge of the corrsponding bin.
+        The right plot, with ``(t0, t1, f0, f1) = (-0.5, 2.5, -0.5, 3.5)``, shows that
+        the bins are centered over the respective values when passing
+        ``center_bins=True``.
+
+        >>> import matplotlib.pyplot as plt
+        >>> import numpy as np
+        >>> from scipy.signal import ShortTimeFFT
+        ...
+        >>> n, m = 12, 6
+        >>> SFT = ShortTimeFFT.from_window('hann', fs=m, nperseg=m, noverlap=0)
+        >>> Sxx = SFT.stft(np.cos(np.arange(n)))  # produces a colorful plot
+        ...
+        >>> fig, axx = plt.subplots(1, 2, tight_layout=True, figsize=(6., 4.))
+        >>> for ax_, center_bins in zip(axx, (False, True)):
+        ...     ax_.imshow(abs(Sxx), origin='lower', interpolation=None, aspect='equal',
+        ...                cmap='viridis', extent=SFT.extent(n, 'tf', center_bins))
+        ...     ax_.set_title(f"{center_bins=}")
+        ...     ax_.set_xlabel(f"Time ({SFT.p_num(n)} points, Δt={SFT.delta_t})")
+        ...     ax_.set_ylabel(f"Frequency ({SFT.f_pts} points, Δf={SFT.delta_f})")
+        ...     ax_.set_xticks(SFT.t(n))  # vertical grid line are timestamps
+        ...     ax_.set_yticks(SFT.f)  # horizontal grid line are frequency values
+        ...     ax_.grid(True)
+        >>> plt.show()
+
+        Note that the step-like behavior with the constant colors is caused by passing
+        ``interpolation=None`` to `~matplotlib.pyplot.imshow`.
+        """
+        if axes_seq not in ('tf', 'ft'):
+            raise ValueError(f"Parameter {axes_seq=} not in ['tf', 'ft']!")
+
+        if self.onesided_fft:
+            q0, q1 = 0, self.f_pts
+        elif self.fft_mode == 'centered':
+            q0 = -(self.mfft // 2)
+            q1 = self.mfft // 2 if self.mfft % 2 == 0 else self.mfft // 2 + 1
+        else:
+            raise ValueError(f"Attribute fft_mode={self.fft_mode} must be " +
+                             "in ['centered', 'onesided', 'onesided2X']")
+
+        p0, p1 = self.p_min, self.p_max(n)  # shorthand
+        if center_bins:
+            t0, t1 = self.delta_t * (p0 - 0.5), self.delta_t * (p1 - 0.5)
+            f0, f1 = self.delta_f * (q0 - 0.5), self.delta_f * (q1 - 0.5)
+        else:
+            t0, t1 = self.delta_t * p0, self.delta_t * p1
+            f0, f1 = self.delta_f * q0, self.delta_f * q1
+        return (t0, t1, f0, f1) if axes_seq == 'tf' else (f0, f1, t0, t1)

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_spectral_py.py

@@ -0,0 +1,2291 @@
+"""Tools for spectral analysis.
+"""
+import numpy as np
+import numpy.typing as npt
+from scipy import fft as sp_fft
+from . import _signaltools
+from .windows import get_window
+from ._arraytools import const_ext, even_ext, odd_ext, zero_ext
+import warnings
+from typing import Literal
+
+
+__all__ = ['periodogram', 'welch', 'lombscargle', 'csd', 'coherence',
+           'spectrogram', 'stft', 'istft', 'check_COLA', 'check_NOLA']
+
+
+def lombscargle(
+    x: npt.ArrayLike,
+    y: npt.ArrayLike,
+    freqs: npt.ArrayLike,
+    precenter: bool = False,
+    normalize: bool | Literal["power", "normalize", "amplitude"] = False,
+    *,
+    weights: npt.NDArray | None = None,
+    floating_mean: bool = False,
+) -> npt.NDArray:
+    """
+    Compute the generalized Lomb-Scargle periodogram.
+
+    The Lomb-Scargle periodogram was developed by Lomb [1]_ and further
+    extended by Scargle [2]_ to find, and test the significance of weak
+    periodic signals with uneven temporal sampling. The algorithm used
+    here is based on a weighted least-squares fit of the form
+    ``y(ω) = a*cos(ω*x) + b*sin(ω*x) + c``, where the fit is calculated for
+    each frequency independently. This algorithm was developed by Zechmeister
+    and Kürster which improves the Lomb-Scargle periodogram by enabling
+    the weighting of individual samples and calculating an unknown y offset
+    (also called a "floating-mean" model) [3]_. For more details, and practical
+    considerations, see the excellent reference on the Lomb-Scargle periodogram [4]_.
+
+    When *normalize* is False (or "power") (default) the computed periodogram
+    is unnormalized, it takes the value ``(A**2) * N/4`` for a harmonic
+    signal with amplitude A for sufficiently large N. Where N is the length of x or y.
+
+    When *normalize* is True (or "normalize") the computed periodogram is normalized
+    by the residuals of the data around a constant reference model (at zero).
+
+    When *normalize* is "amplitude" the computed periodogram is the complex
+    representation of the amplitude and phase.
+
+    Input arrays should be 1-D of a real floating data type, which are converted into
+    float64 arrays before processing.
+
+    Parameters
+    ----------
+    x : array_like
+        Sample times.
+    y : array_like
+        Measurement values. Values are assumed to have a baseline of ``y = 0``. If
+        there is a possibility of a y offset, it is recommended to set `floating_mean`
+        to True.
+    freqs : array_like
+        Angular frequencies (e.g., having unit rad/s=2π/s for `x` having unit s) for
+        output periodogram. Frequencies are normally >= 0, as any peak at ``-freq`` will
+        also exist at ``+freq``.
+    precenter : bool, optional
+        Pre-center measurement values by subtracting the mean, if True. This is
+        a legacy parameter and unnecessary if `floating_mean` is True.
+    normalize : bool | str, optional
+        Compute normalized or complex (amplitude + phase) periodogram.
+        Valid options are: ``False``/``"power"``, ``True``/``"normalize"``, or
+        ``"amplitude"``.
+    weights : array_like, optional
+        Weights for each sample. Weights must be nonnegative.
+    floating_mean : bool, optional
+        Determines a y offset for each frequency independently, if True.
+        Else the y offset is assumed to be `0`.
+
+    Returns
+    -------
+    pgram : array_like
+        Lomb-Scargle periodogram.
+
+    Raises
+    ------
+    ValueError
+        If any of the input arrays x, y, freqs, or weights are not 1D, or if any are
+        zero length. Or, if the input arrays x, y, and weights do not have the same
+        shape as each other.
+    ValueError
+        If any weight is < 0, or the sum of the weights is <= 0.
+    ValueError
+        If the normalize parameter is not one of the allowed options.
+
+    See Also
+    --------
+    periodogram: Power spectral density using a periodogram
+    welch: Power spectral density by Welch's method
+    csd: Cross spectral density by Welch's method
+
+    Notes
+    -----
+    The algorithm used will not automatically account for any unknown y offset, unless
+    floating_mean is True. Therefore, for most use cases, if there is a possibility of
+    a y offset, it is recommended to set floating_mean to True. If precenter is True,
+    it performs the operation ``y -= y.mean()``. However, precenter is a legacy
+    parameter, and unnecessary when floating_mean is True. Furthermore, the mean
+    removed by precenter does not account for sample weights, nor will it correct for
+    any bias due to consistently missing observations at peaks and/or troughs. When the
+    normalize parameter is "amplitude", for any frequency in freqs that is below
+    ``(2*pi)/(x.max() - x.min())``, the predicted amplitude will tend towards infinity.
+    The concept of a "Nyquist frequency" limit (see Nyquist-Shannon sampling theorem)
+    is not generally applicable to unevenly sampled data. Therefore, with unevenly
+    sampled data, valid frequencies in freqs can often be much higher than expected.
+
+    References
+    ----------
+    .. [1] N.R. Lomb "Least-squares frequency analysis of unequally spaced
+           data", Astrophysics and Space Science, vol 39, pp. 447-462, 1976
+           :doi:`10.1007/bf00648343`
+
+    .. [2] J.D. Scargle "Studies in astronomical time series analysis. II -
+           Statistical aspects of spectral analysis of unevenly spaced data",
+           The Astrophysical Journal, vol 263, pp. 835-853, 1982
+           :doi:`10.1086/160554`
+
+    .. [3] M. Zechmeister and M. Kürster, "The generalised Lomb-Scargle periodogram.
+           A new formalism for the floating-mean and Keplerian periodograms,"
+           Astronomy and Astrophysics, vol. 496, pp. 577-584, 2009
+           :doi:`10.1051/0004-6361:200811296`
+
+    .. [4] J.T. VanderPlas, "Understanding the Lomb-Scargle Periodogram,"
+           The Astrophysical Journal Supplement Series, vol. 236, no. 1, p. 16,
+           May 2018
+           :doi:`10.3847/1538-4365/aab766`
+
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> rng = np.random.default_rng()
+
+    First define some input parameters for the signal:
+
+    >>> A = 2.  # amplitude
+    >>> c = 2.  # offset
+    >>> w0 = 1.  # rad/sec
+    >>> nin = 150
+    >>> nout = 1002
+
+    Randomly generate sample times:
+
+    >>> x = rng.uniform(0, 10*np.pi, nin)
+
+    Plot a sine wave for the selected times:
+
+    >>> y = A * np.cos(w0*x) + c
+
+    Define the array of frequencies for which to compute the periodogram:
+
+    >>> w = np.linspace(0.25, 10, nout)
+
+    Calculate Lomb-Scargle periodogram for each of the normalize options:
+
+    >>> from scipy.signal import lombscargle
+    >>> pgram_power = lombscargle(x, y, w, normalize=False)
+    >>> pgram_norm = lombscargle(x, y, w, normalize=True)
+    >>> pgram_amp = lombscargle(x, y, w, normalize='amplitude')
+    ...
+    >>> pgram_power_f = lombscargle(x, y, w, normalize=False, floating_mean=True)
+    >>> pgram_norm_f = lombscargle(x, y, w, normalize=True, floating_mean=True)
+    >>> pgram_amp_f = lombscargle(x, y, w, normalize='amplitude', floating_mean=True)
+
+    Now make a plot of the input data:
+
+    >>> import matplotlib.pyplot as plt
+    >>> fig, (ax_t, ax_p, ax_n, ax_a) = plt.subplots(4, 1, figsize=(5, 6))
+    >>> ax_t.plot(x, y, 'b+')
+    >>> ax_t.set_xlabel('Time [s]')
+    >>> ax_t.set_ylabel('Amplitude')
+
+    Then plot the periodogram for each of the normalize options, as well as with and
+    without floating_mean=True:
+
+    >>> ax_p.plot(w, pgram_power, label='default')
+    >>> ax_p.plot(w, pgram_power_f, label='floating_mean=True')
+    >>> ax_p.set_xlabel('Angular frequency [rad/s]')
+    >>> ax_p.set_ylabel('Power')
+    >>> ax_p.legend(prop={'size': 7})
+    ...
+    >>> ax_n.plot(w, pgram_norm, label='default')
+    >>> ax_n.plot(w, pgram_norm_f, label='floating_mean=True')
+    >>> ax_n.set_xlabel('Angular frequency [rad/s]')
+    >>> ax_n.set_ylabel('Normalized')
+    >>> ax_n.legend(prop={'size': 7})
+    ...
+    >>> ax_a.plot(w, np.abs(pgram_amp), label='default')
+    >>> ax_a.plot(w, np.abs(pgram_amp_f), label='floating_mean=True')
+    >>> ax_a.set_xlabel('Angular frequency [rad/s]')
+    >>> ax_a.set_ylabel('Amplitude')
+    >>> ax_a.legend(prop={'size': 7})
+    ...
+    >>> plt.tight_layout()
+    >>> plt.show()
+
+    """
+
+    # if no weights are provided, assume all data points are equally important
+    if weights is None:
+        weights = np.ones_like(y, dtype=np.float64)
+    else:
+        # if provided, make sure weights is an array and cast to float64
+        weights = np.asarray(weights, dtype=np.float64)
+
+    # make sure other inputs are arrays and cast to float64
+    # done before validation, in case they were not arrays
+    x = np.asarray(x, dtype=np.float64)
+    y = np.asarray(y, dtype=np.float64)
+    freqs = np.asarray(freqs, dtype=np.float64)
+
+    # validate input shapes
+    if not (x.ndim == 1 and x.size > 0 and x.shape == y.shape == weights.shape):
+        raise ValueError("Parameters x, y, weights must be 1-D arrays of "
+                         "equal non-zero length!")
+    if not (freqs.ndim == 1 and freqs.size > 0):
+        raise ValueError("Parameter freqs must be a 1-D array of non-zero length!")
+
+    # validate weights
+    if not (np.all(weights >= 0) and np.sum(weights) > 0):
+        raise ValueError("Parameter weights must have only non-negative entries "
+                         "which sum to a positive value!")
+
+    # validate normalize parameter
+    if isinstance(normalize, bool):
+        # if bool, convert to str literal
+        normalize = "normalize" if normalize else "power"
+
+    if normalize not in ["power", "normalize", "amplitude"]:
+        raise ValueError(
+            "Normalize must be: False (or 'power'), True (or 'normalize'), "
+            "or 'amplitude'."
+        )
+
+    # weight vector must sum to 1
+    weights *= 1.0 / weights.sum()
+
+    # if requested, perform precenter
+    if precenter:
+        y -= y.mean()
+
+    # transform arrays
+    # row vector
+    freqs = freqs.reshape(1, -1)
+    # column vectors
+    x = x.reshape(-1, 1)
+    y = y.reshape(-1, 1)
+    weights = weights.reshape(-1, 1)
+
+    # store frequent intermediates
+    weights_y = weights * y
+    freqst = freqs * x
+    coswt = np.cos(freqst)
+    sinwt = np.sin(freqst)
+
+    Y = np.dot(weights.T, y)  # Eq. 7
+    CC = np.dot(weights.T, coswt * coswt)  # Eq. 13
+    SS = 1.0 - CC  # trig identity: S^2 = 1 - C^2  Eq.14
+    CS = np.dot(weights.T, coswt * sinwt)  # Eq. 15
+
+    if floating_mean:
+        C = np.dot(weights.T, coswt)  # Eq. 8
+        S = np.dot(weights.T, sinwt)  # Eq. 9
+        CC -= C * C  # Eq. 13
+        SS -= S * S  # Eq. 14
+        CS -= C * S  # Eq. 15
+
+    # calculate tau (phase offset to eliminate CS variable)
+    tau = 0.5 * np.arctan2(2.0 * CS, CC - SS)  # Eq. 19
+    freqst_tau = freqst - tau
+
+    # coswt and sinwt are now offset by tau, which eliminates CS
+    coswt_tau = np.cos(freqst_tau)
+    sinwt_tau = np.sin(freqst_tau)
+
+    YC = np.dot(weights_y.T, coswt_tau)  # Eq. 11
+    YS = np.dot(weights_y.T, sinwt_tau)  # Eq. 12
+    CC = np.dot(weights.T, coswt_tau * coswt_tau)  # Eq. 13, CC range is [0.5, 1.0]
+    SS = 1.0 - CC  # trig identity: S^2 = 1 - C^2    Eq. 14, SS range is [0.0, 0.5]
+
+    if floating_mean:
+        C = np.dot(weights.T, coswt_tau)  # Eq. 8
+        S = np.dot(weights.T, sinwt_tau)  # Eq. 9
+        YC -= Y * C  # Eq. 11
+        YS -= Y * S  # Eq. 12
+        CC -= C * C  # Eq. 13, CC range is now [0.0, 1.0]
+        SS -= S * S  # Eq. 14, SS range is now [0.0, 0.5]
+
+    # to prevent division by zero errors with a and b, as well as correcting for
+    # numerical precision errors that lead to CC or SS being approximately -0.0,
+    # make sure CC and SS are both > 0
+    epsneg = np.finfo(dtype=y.dtype).epsneg
+    CC[CC < epsneg] = epsneg
+    SS[SS < epsneg] = epsneg
+
+    # calculate a and b
+    # where: y(w) = a*cos(w) + b*sin(w) + c
+    a = YC / CC  # Eq. A.4 and 6, eliminating CS
+    b = YS / SS  # Eq. A.4 and 6, eliminating CS
+    # c = Y - a * C - b * S
+
+    # store final value as power in A^2 (i.e., (y units)^2)
+    pgram = 2.0 * (a * YC + b * YS)
+
+    # squeeze back to a vector
+    pgram = np.squeeze(pgram)
+
+    if normalize == "power":  # (default)
+        # return the legacy power units ((A**2) * N/4)
+
+        pgram *= float(x.shape[0]) / 4.0
+
+    elif normalize == "normalize":
+        # return the normalized power (power at current frequency wrt the entire signal)
+        # range will be [0, 1]
+
+        YY = np.dot(weights_y.T, y)  # Eq. 10
+        if floating_mean:
+            YY -= Y * Y  # Eq. 10
+
+        pgram *= 0.5 / np.squeeze(YY)  # Eq. 20
+
+    else:  # normalize == "amplitude":
+        # return the complex representation of the best-fit amplitude and phase
+
+        # squeeze back to vectors
+        a = np.squeeze(a)
+        b = np.squeeze(b)
+        tau = np.squeeze(tau)
+
+        # calculate the complex representation, and correct for tau rotation
+        pgram = (a + 1j * b) * np.exp(1j * tau)
+
+    return pgram
+
+
+def periodogram(x, fs=1.0, window='boxcar', nfft=None, detrend='constant',
+                return_onesided=True, scaling='density', axis=-1):
+    """
+    Estimate power spectral density using a periodogram.
+
+    Parameters
+    ----------
+    x : array_like
+        Time series of measurement values
+    fs : float, optional
+        Sampling frequency of the `x` time series. Defaults to 1.0.
+    window : str or tuple or array_like, optional
+        Desired window to use. If `window` is a string or tuple, it is
+        passed to `get_window` to generate the window values, which are
+        DFT-even by default. See `get_window` for a list of windows and
+        required parameters. If `window` is array_like it will be used
+        directly as the window and its length must be equal to the length
+        of the axis over which the periodogram is computed. Defaults
+        to 'boxcar'.
+    nfft : int, optional
+        Length of the FFT used. If `None` the length of `x` will be
+        used.
+    detrend : str or function or `False`, optional
+        Specifies how to detrend each segment. If `detrend` is a
+        string, it is passed as the `type` argument to the `detrend`
+        function. If it is a function, it takes a segment and returns a
+        detrended segment. If `detrend` is `False`, no detrending is
+        done. Defaults to 'constant'.
+    return_onesided : bool, optional
+        If `True`, return a one-sided spectrum for real data. If
+        `False` return a two-sided spectrum. Defaults to `True`, but for
+        complex data, a two-sided spectrum is always returned.
+    scaling : { 'density', 'spectrum' }, optional
+        Selects between computing the power spectral density ('density')
+        where `Pxx` has units of V**2/Hz and computing the squared magnitude
+        spectrum ('spectrum') where `Pxx` has units of V**2, if `x`
+        is measured in V and `fs` is measured in Hz. Defaults to
+        'density'
+    axis : int, optional
+        Axis along which the periodogram is computed; the default is
+        over the last axis (i.e. ``axis=-1``).
+
+    Returns
+    -------
+    f : ndarray
+        Array of sample frequencies.
+    Pxx : ndarray
+        Power spectral density or power spectrum of `x`.
+
+    See Also
+    --------
+    welch: Estimate power spectral density using Welch's method
+    lombscargle: Lomb-Scargle periodogram for unevenly sampled data
+
+    Notes
+    -----
+    Consult the :ref:`tutorial_SpectralAnalysis` section of the :ref:`user_guide`
+    for a discussion of the scalings of the power spectral density and
+    the magnitude (squared) spectrum.
+
+    .. versionadded:: 0.12.0
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> import matplotlib.pyplot as plt
+    >>> rng = np.random.default_rng()
+
+    Generate a test signal, a 2 Vrms sine wave at 1234 Hz, corrupted by
+    0.001 V**2/Hz of white noise sampled at 10 kHz.
+
+    >>> fs = 10e3
+    >>> N = 1e5
+    >>> amp = 2*np.sqrt(2)
+    >>> freq = 1234.0
+    >>> noise_power = 0.001 * fs / 2
+    >>> time = np.arange(N) / fs
+    >>> x = amp*np.sin(2*np.pi*freq*time)
+    >>> x += rng.normal(scale=np.sqrt(noise_power), size=time.shape)
+
+    Compute and plot the power spectral density.
+
+    >>> f, Pxx_den = signal.periodogram(x, fs)
+    >>> plt.semilogy(f, Pxx_den)
+    >>> plt.ylim([1e-7, 1e2])
+    >>> plt.xlabel('frequency [Hz]')
+    >>> plt.ylabel('PSD [V**2/Hz]')
+    >>> plt.show()
+
+    If we average the last half of the spectral density, to exclude the
+    peak, we can recover the noise power on the signal.
+
+    >>> np.mean(Pxx_den[25000:])
+    0.000985320699252543
+
+    Now compute and plot the power spectrum.
+
+    >>> f, Pxx_spec = signal.periodogram(x, fs, 'flattop', scaling='spectrum')
+    >>> plt.figure()
+    >>> plt.semilogy(f, np.sqrt(Pxx_spec))
+    >>> plt.ylim([1e-4, 1e1])
+    >>> plt.xlabel('frequency [Hz]')
+    >>> plt.ylabel('Linear spectrum [V RMS]')
+    >>> plt.show()
+
+    The peak height in the power spectrum is an estimate of the RMS
+    amplitude.
+
+    >>> np.sqrt(Pxx_spec.max())
+    2.0077340678640727
+
+    """
+    x = np.asarray(x)
+
+    if x.size == 0:
+        return np.empty(x.shape), np.empty(x.shape)
+
+    if window is None:
+        window = 'boxcar'
+
+    if nfft is None:
+        nperseg = x.shape[axis]
+    elif nfft == x.shape[axis]:
+        nperseg = nfft
+    elif nfft > x.shape[axis]:
+        nperseg = x.shape[axis]
+    elif nfft < x.shape[axis]:
+        s = [np.s_[:]]*len(x.shape)
+        s[axis] = np.s_[:nfft]
+        x = x[tuple(s)]
+        nperseg = nfft
+        nfft = None
+
+    if hasattr(window, 'size'):
+        if window.size != nperseg:
+            raise ValueError('the size of the window must be the same size '
+                             'of the input on the specified axis')
+
+    return welch(x, fs=fs, window=window, nperseg=nperseg, noverlap=0,
+                 nfft=nfft, detrend=detrend, return_onesided=return_onesided,
+                 scaling=scaling, axis=axis)
+
+
+def welch(x, fs=1.0, window='hann', nperseg=None, noverlap=None, nfft=None,
+          detrend='constant', return_onesided=True, scaling='density',
+          axis=-1, average='mean'):
+    r"""
+    Estimate power spectral density using Welch's method.
+
+    Welch's method [1]_ computes an estimate of the power spectral
+    density by dividing the data into overlapping segments, computing a
+    modified periodogram for each segment and averaging the
+    periodograms.
+
+    Parameters
+    ----------
+    x : array_like
+        Time series of measurement values
+    fs : float, optional
+        Sampling frequency of the `x` time series. Defaults to 1.0.
+    window : str or tuple or array_like, optional
+        Desired window to use. If `window` is a string or tuple, it is
+        passed to `get_window` to generate the window values, which are
+        DFT-even by default. See `get_window` for a list of windows and
+        required parameters. If `window` is array_like it will be used
+        directly as the window and its length must be nperseg. Defaults
+        to a Hann window.
+    nperseg : int, optional
+        Length of each segment. Defaults to None, but if window is str or
+        tuple, is set to 256, and if window is array_like, is set to the
+        length of the window.
+    noverlap : int, optional
+        Number of points to overlap between segments. If `None`,
+        ``noverlap = nperseg // 2``. Defaults to `None`.
+    nfft : int, optional
+        Length of the FFT used, if a zero padded FFT is desired. If
+        `None`, the FFT length is `nperseg`. Defaults to `None`.
+    detrend : str or function or `False`, optional
+        Specifies how to detrend each segment. If `detrend` is a
+        string, it is passed as the `type` argument to the `detrend`
+        function. If it is a function, it takes a segment and returns a
+        detrended segment. If `detrend` is `False`, no detrending is
+        done. Defaults to 'constant'.
+    return_onesided : bool, optional
+        If `True`, return a one-sided spectrum for real data. If
+        `False` return a two-sided spectrum. Defaults to `True`, but for
+        complex data, a two-sided spectrum is always returned.
+    scaling : { 'density', 'spectrum' }, optional
+        Selects between computing the power spectral density ('density')
+        where `Pxx` has units of V**2/Hz and computing the squared magnitude
+        spectrum ('spectrum') where `Pxx` has units of V**2, if `x`
+        is measured in V and `fs` is measured in Hz. Defaults to
+        'density'
+    axis : int, optional
+        Axis along which the periodogram is computed; the default is
+        over the last axis (i.e. ``axis=-1``).
+    average : { 'mean', 'median' }, optional
+        Method to use when averaging periodograms. Defaults to 'mean'.
+
+        .. versionadded:: 1.2.0
+
+    Returns
+    -------
+    f : ndarray
+        Array of sample frequencies.
+    Pxx : ndarray
+        Power spectral density or power spectrum of x.
+
+    See Also
+    --------
+    periodogram: Simple, optionally modified periodogram
+    lombscargle: Lomb-Scargle periodogram for unevenly sampled data
+
+    Notes
+    -----
+    An appropriate amount of overlap will depend on the choice of window
+    and on your requirements. For the default Hann window an overlap of
+    50% is a reasonable trade off between accurately estimating the
+    signal power, while not over counting any of the data. Narrower
+    windows may require a larger overlap.
+
+    If `noverlap` is 0, this method is equivalent to Bartlett's method
+    [2]_.
+
+    Consult the :ref:`tutorial_SpectralAnalysis` section of the :ref:`user_guide`
+    for a discussion of the scalings of the power spectral density and
+    the (squared) magnitude spectrum.
+
+    .. versionadded:: 0.12.0
+
+    References
+    ----------
+    .. [1] P. Welch, "The use of the fast Fourier transform for the
+           estimation of power spectra: A method based on time averaging
+           over short, modified periodograms", IEEE Trans. Audio
+           Electroacoust. vol. 15, pp. 70-73, 1967.
+    .. [2] M.S. Bartlett, "Periodogram Analysis and Continuous Spectra",
+           Biometrika, vol. 37, pp. 1-16, 1950.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> import matplotlib.pyplot as plt
+    >>> rng = np.random.default_rng()
+
+    Generate a test signal, a 2 Vrms sine wave at 1234 Hz, corrupted by
+    0.001 V**2/Hz of white noise sampled at 10 kHz.
+
+    >>> fs = 10e3
+    >>> N = 1e5
+    >>> amp = 2*np.sqrt(2)
+    >>> freq = 1234.0
+    >>> noise_power = 0.001 * fs / 2
+    >>> time = np.arange(N) / fs
+    >>> x = amp*np.sin(2*np.pi*freq*time)
+    >>> x += rng.normal(scale=np.sqrt(noise_power), size=time.shape)
+
+    Compute and plot the power spectral density.
+
+    >>> f, Pxx_den = signal.welch(x, fs, nperseg=1024)
+    >>> plt.semilogy(f, Pxx_den)
+    >>> plt.ylim([0.5e-3, 1])
+    >>> plt.xlabel('frequency [Hz]')
+    >>> plt.ylabel('PSD [V**2/Hz]')
+    >>> plt.show()
+
+    If we average the last half of the spectral density, to exclude the
+    peak, we can recover the noise power on the signal.
+
+    >>> np.mean(Pxx_den[256:])
+    0.0009924865443739191
+
+    Now compute and plot the power spectrum.
+
+    >>> f, Pxx_spec = signal.welch(x, fs, 'flattop', 1024, scaling='spectrum')
+    >>> plt.figure()
+    >>> plt.semilogy(f, np.sqrt(Pxx_spec))
+    >>> plt.xlabel('frequency [Hz]')
+    >>> plt.ylabel('Linear spectrum [V RMS]')
+    >>> plt.show()
+
+    The peak height in the power spectrum is an estimate of the RMS
+    amplitude.
+
+    >>> np.sqrt(Pxx_spec.max())
+    2.0077340678640727
+
+    If we now introduce a discontinuity in the signal, by increasing the
+    amplitude of a small portion of the signal by 50, we can see the
+    corruption of the mean average power spectral density, but using a
+    median average better estimates the normal behaviour.
+
+    >>> x[int(N//2):int(N//2)+10] *= 50.
+    >>> f, Pxx_den = signal.welch(x, fs, nperseg=1024)
+    >>> f_med, Pxx_den_med = signal.welch(x, fs, nperseg=1024, average='median')
+    >>> plt.semilogy(f, Pxx_den, label='mean')
+    >>> plt.semilogy(f_med, Pxx_den_med, label='median')
+    >>> plt.ylim([0.5e-3, 1])
+    >>> plt.xlabel('frequency [Hz]')
+    >>> plt.ylabel('PSD [V**2/Hz]')
+    >>> plt.legend()
+    >>> plt.show()
+
+    """
+    freqs, Pxx = csd(x, x, fs=fs, window=window, nperseg=nperseg,
+                     noverlap=noverlap, nfft=nfft, detrend=detrend,
+                     return_onesided=return_onesided, scaling=scaling,
+                     axis=axis, average=average)
+
+    return freqs, Pxx.real
+
+
+def csd(x, y, fs=1.0, window='hann', nperseg=None, noverlap=None, nfft=None,
+        detrend='constant', return_onesided=True, scaling='density',
+        axis=-1, average='mean'):
+    r"""
+    Estimate the cross power spectral density, Pxy, using Welch's method.
+
+    Parameters
+    ----------
+    x : array_like
+        Time series of measurement values
+    y : array_like
+        Time series of measurement values
+    fs : float, optional
+        Sampling frequency of the `x` and `y` time series. Defaults
+        to 1.0.
+    window : str or tuple or array_like, optional
+        Desired window to use. If `window` is a string or tuple, it is
+        passed to `get_window` to generate the window values, which are
+        DFT-even by default. See `get_window` for a list of windows and
+        required parameters. If `window` is array_like it will be used
+        directly as the window and its length must be nperseg. Defaults
+        to a Hann window.
+    nperseg : int, optional
+        Length of each segment. Defaults to None, but if window is str or
+        tuple, is set to 256, and if window is array_like, is set to the
+        length of the window.
+    noverlap: int, optional
+        Number of points to overlap between segments. If `None`,
+        ``noverlap = nperseg // 2``. Defaults to `None`.
+    nfft : int, optional
+        Length of the FFT used, if a zero padded FFT is desired. If
+        `None`, the FFT length is `nperseg`. Defaults to `None`.
+    detrend : str or function or `False`, optional
+        Specifies how to detrend each segment. If `detrend` is a
+        string, it is passed as the `type` argument to the `detrend`
+        function. If it is a function, it takes a segment and returns a
+        detrended segment. If `detrend` is `False`, no detrending is
+        done. Defaults to 'constant'.
+    return_onesided : bool, optional
+        If `True`, return a one-sided spectrum for real data. If
+        `False` return a two-sided spectrum. Defaults to `True`, but for
+        complex data, a two-sided spectrum is always returned.
+    scaling : { 'density', 'spectrum' }, optional
+        Selects between computing the cross spectral density ('density')
+        where `Pxy` has units of V**2/Hz and computing the cross spectrum
+        ('spectrum') where `Pxy` has units of V**2, if `x` and `y` are
+        measured in V and `fs` is measured in Hz. Defaults to 'density'
+    axis : int, optional
+        Axis along which the CSD is computed for both inputs; the
+        default is over the last axis (i.e. ``axis=-1``).
+    average : { 'mean', 'median' }, optional
+        Method to use when averaging periodograms. If the spectrum is
+        complex, the average is computed separately for the real and
+        imaginary parts. Defaults to 'mean'.
+
+        .. versionadded:: 1.2.0
+
+    Returns
+    -------
+    f : ndarray
+        Array of sample frequencies.
+    Pxy : ndarray
+        Cross spectral density or cross power spectrum of x,y.
+
+    See Also
+    --------
+    periodogram: Simple, optionally modified periodogram
+    lombscargle: Lomb-Scargle periodogram for unevenly sampled data
+    welch: Power spectral density by Welch's method. [Equivalent to
+           csd(x,x)]
+    coherence: Magnitude squared coherence by Welch's method.
+
+    Notes
+    -----
+    By convention, Pxy is computed with the conjugate FFT of X
+    multiplied by the FFT of Y.
+
+    If the input series differ in length, the shorter series will be
+    zero-padded to match.
+
+    An appropriate amount of overlap will depend on the choice of window
+    and on your requirements. For the default Hann window an overlap of
+    50% is a reasonable trade off between accurately estimating the
+    signal power, while not over counting any of the data. Narrower
+    windows may require a larger overlap.
+
+    Consult the :ref:`tutorial_SpectralAnalysis` section of the :ref:`user_guide`
+    for a discussion of the scalings of a spectral density and an (amplitude) spectrum.
+
+    .. versionadded:: 0.16.0
+
+    References
+    ----------
+    .. [1] P. Welch, "The use of the fast Fourier transform for the
+           estimation of power spectra: A method based on time averaging
+           over short, modified periodograms", IEEE Trans. Audio
+           Electroacoust. vol. 15, pp. 70-73, 1967.
+    .. [2] Rabiner, Lawrence R., and B. Gold. "Theory and Application of
+           Digital Signal Processing" Prentice-Hall, pp. 414-419, 1975
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> import matplotlib.pyplot as plt
+    >>> rng = np.random.default_rng()
+
+    Generate two test signals with some common features.
+
+    >>> fs = 10e3
+    >>> N = 1e5
+    >>> amp = 20
+    >>> freq = 1234.0
+    >>> noise_power = 0.001 * fs / 2
+    >>> time = np.arange(N) / fs
+    >>> b, a = signal.butter(2, 0.25, 'low')
+    >>> x = rng.normal(scale=np.sqrt(noise_power), size=time.shape)
+    >>> y = signal.lfilter(b, a, x)
+    >>> x += amp*np.sin(2*np.pi*freq*time)
+    >>> y += rng.normal(scale=0.1*np.sqrt(noise_power), size=time.shape)
+
+    Compute and plot the magnitude of the cross spectral density.
+
+    >>> f, Pxy = signal.csd(x, y, fs, nperseg=1024)
+    >>> plt.semilogy(f, np.abs(Pxy))
+    >>> plt.xlabel('frequency [Hz]')
+    >>> plt.ylabel('CSD [V**2/Hz]')
+    >>> plt.show()
+
+    """
+    freqs, _, Pxy = _spectral_helper(x, y, fs, window, nperseg, noverlap,
+                                     nfft, detrend, return_onesided, scaling,
+                                     axis, mode='psd')
+
+    # Average over windows.
+    if len(Pxy.shape) >= 2 and Pxy.size > 0:
+        if Pxy.shape[-1] > 1:
+            if average == 'median':
+                # np.median must be passed real arrays for the desired result
+                bias = _median_bias(Pxy.shape[-1])
+                if np.iscomplexobj(Pxy):
+                    Pxy = (np.median(np.real(Pxy), axis=-1)
+                           + 1j * np.median(np.imag(Pxy), axis=-1))
+                else:
+                    Pxy = np.median(Pxy, axis=-1)
+                Pxy /= bias
+            elif average == 'mean':
+                Pxy = Pxy.mean(axis=-1)
+            else:
+                raise ValueError(f'average must be "median" or "mean", got {average}')
+        else:
+            Pxy = np.reshape(Pxy, Pxy.shape[:-1])
+
+    return freqs, Pxy
+
+
+def spectrogram(x, fs=1.0, window=('tukey', .25), nperseg=None, noverlap=None,
+                nfft=None, detrend='constant', return_onesided=True,
+                scaling='density', axis=-1, mode='psd'):
+    """Compute a spectrogram with consecutive Fourier transforms (legacy function).
+
+    Spectrograms can be used as a way of visualizing the change of a
+    nonstationary signal's frequency content over time.
+
+    .. legacy:: function
+
+        :class:`ShortTimeFFT` is a newer STFT / ISTFT implementation with more
+        features also including a :meth:`~ShortTimeFFT.spectrogram` method.
+        A :ref:`comparison <tutorial_stft_legacy_stft>` between the
+        implementations can be found in the :ref:`tutorial_stft` section of
+        the :ref:`user_guide`.
+
+    Parameters
+    ----------
+    x : array_like
+        Time series of measurement values
+    fs : float, optional
+        Sampling frequency of the `x` time series. Defaults to 1.0.
+    window : str or tuple or array_like, optional
+        Desired window to use. If `window` is a string or tuple, it is
+        passed to `get_window` to generate the window values, which are
+        DFT-even by default. See `get_window` for a list of windows and
+        required parameters. If `window` is array_like it will be used
+        directly as the window and its length must be nperseg.
+        Defaults to a Tukey window with shape parameter of 0.25.
+    nperseg : int, optional
+        Length of each segment. Defaults to None, but if window is str or
+        tuple, is set to 256, and if window is array_like, is set to the
+        length of the window.
+    noverlap : int, optional
+        Number of points to overlap between segments. If `None`,
+        ``noverlap = nperseg // 8``. Defaults to `None`.
+    nfft : int, optional
+        Length of the FFT used, if a zero padded FFT is desired. If
+        `None`, the FFT length is `nperseg`. Defaults to `None`.
+    detrend : str or function or `False`, optional
+        Specifies how to detrend each segment. If `detrend` is a
+        string, it is passed as the `type` argument to the `detrend`
+        function. If it is a function, it takes a segment and returns a
+        detrended segment. If `detrend` is `False`, no detrending is
+        done. Defaults to 'constant'.
+    return_onesided : bool, optional
+        If `True`, return a one-sided spectrum for real data. If
+        `False` return a two-sided spectrum. Defaults to `True`, but for
+        complex data, a two-sided spectrum is always returned.
+    scaling : { 'density', 'spectrum' }, optional
+        Selects between computing the power spectral density ('density')
+        where `Sxx` has units of V**2/Hz and computing the power
+        spectrum ('spectrum') where `Sxx` has units of V**2, if `x`
+        is measured in V and `fs` is measured in Hz. Defaults to
+        'density'.
+    axis : int, optional
+        Axis along which the spectrogram is computed; the default is over
+        the last axis (i.e. ``axis=-1``).
+    mode : str, optional
+        Defines what kind of return values are expected. Options are
+        ['psd', 'complex', 'magnitude', 'angle', 'phase']. 'complex' is
+        equivalent to the output of `stft` with no padding or boundary
+        extension. 'magnitude' returns the absolute magnitude of the
+        STFT. 'angle' and 'phase' return the complex angle of the STFT,
+        with and without unwrapping, respectively.
+
+    Returns
+    -------
+    f : ndarray
+        Array of sample frequencies.
+    t : ndarray
+        Array of segment times.
+    Sxx : ndarray
+        Spectrogram of x. By default, the last axis of Sxx corresponds
+        to the segment times.
+
+    See Also
+    --------
+    periodogram: Simple, optionally modified periodogram
+    lombscargle: Lomb-Scargle periodogram for unevenly sampled data
+    welch: Power spectral density by Welch's method.
+    csd: Cross spectral density by Welch's method.
+    ShortTimeFFT: Newer STFT/ISTFT implementation providing more features,
+                  which also includes a :meth:`~ShortTimeFFT.spectrogram`
+                  method.
+
+    Notes
+    -----
+    An appropriate amount of overlap will depend on the choice of window
+    and on your requirements. In contrast to welch's method, where the
+    entire data stream is averaged over, one may wish to use a smaller
+    overlap (or perhaps none at all) when computing a spectrogram, to
+    maintain some statistical independence between individual segments.
+    It is for this reason that the default window is a Tukey window with
+    1/8th of a window's length overlap at each end.
+
+
+    .. versionadded:: 0.16.0
+
+    References
+    ----------
+    .. [1] Oppenheim, Alan V., Ronald W. Schafer, John R. Buck
+           "Discrete-Time Signal Processing", Prentice Hall, 1999.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> from scipy.fft import fftshift
+    >>> import matplotlib.pyplot as plt
+    >>> rng = np.random.default_rng()
+
+    Generate a test signal, a 2 Vrms sine wave whose frequency is slowly
+    modulated around 3kHz, corrupted by white noise of exponentially
+    decreasing magnitude sampled at 10 kHz.
+
+    >>> fs = 10e3
+    >>> N = 1e5
+    >>> amp = 2 * np.sqrt(2)
+    >>> noise_power = 0.01 * fs / 2
+    >>> time = np.arange(N) / float(fs)
+    >>> mod = 500*np.cos(2*np.pi*0.25*time)
+    >>> carrier = amp * np.sin(2*np.pi*3e3*time + mod)
+    >>> noise = rng.normal(scale=np.sqrt(noise_power), size=time.shape)
+    >>> noise *= np.exp(-time/5)
+    >>> x = carrier + noise
+
+    Compute and plot the spectrogram.
+
+    >>> f, t, Sxx = signal.spectrogram(x, fs)
+    >>> plt.pcolormesh(t, f, Sxx, shading='gouraud')
+    >>> plt.ylabel('Frequency [Hz]')
+    >>> plt.xlabel('Time [sec]')
+    >>> plt.show()
+
+    Note, if using output that is not one sided, then use the following:
+
+    >>> f, t, Sxx = signal.spectrogram(x, fs, return_onesided=False)
+    >>> plt.pcolormesh(t, fftshift(f), fftshift(Sxx, axes=0), shading='gouraud')
+    >>> plt.ylabel('Frequency [Hz]')
+    >>> plt.xlabel('Time [sec]')
+    >>> plt.show()
+
+    """
+    modelist = ['psd', 'complex', 'magnitude', 'angle', 'phase']
+    if mode not in modelist:
+        raise ValueError(f'unknown value for mode {mode}, must be one of {modelist}')
+
+    # need to set default for nperseg before setting default for noverlap below
+    window, nperseg = _triage_segments(window, nperseg,
+                                       input_length=x.shape[axis])
+
+    # Less overlap than welch, so samples are more statistically independent
+    if noverlap is None:
+        noverlap = nperseg // 8
+
+    if mode == 'psd':
+        freqs, time, Sxx = _spectral_helper(x, x, fs, window, nperseg,
+                                            noverlap, nfft, detrend,
+                                            return_onesided, scaling, axis,
+                                            mode='psd')
+
+    else:
+        freqs, time, Sxx = _spectral_helper(x, x, fs, window, nperseg,
+                                            noverlap, nfft, detrend,
+                                            return_onesided, scaling, axis,
+                                            mode='stft')
+
+        if mode == 'magnitude':
+            Sxx = np.abs(Sxx)
+        elif mode in ['angle', 'phase']:
+            Sxx = np.angle(Sxx)
+            if mode == 'phase':
+                # Sxx has one additional dimension for time strides
+                if axis < 0:
+                    axis -= 1
+                Sxx = np.unwrap(Sxx, axis=axis)
+
+        # mode =='complex' is same as `stft`, doesn't need modification
+
+    return freqs, time, Sxx
+
+
+def check_COLA(window, nperseg, noverlap, tol=1e-10):
+    r"""Check whether the Constant OverLap Add (COLA) constraint is met.
+
+    Parameters
+    ----------
+    window : str or tuple or array_like
+        Desired window to use. If `window` is a string or tuple, it is
+        passed to `get_window` to generate the window values, which are
+        DFT-even by default. See `get_window` for a list of windows and
+        required parameters. If `window` is array_like it will be used
+        directly as the window and its length must be nperseg.
+    nperseg : int
+        Length of each segment.
+    noverlap : int
+        Number of points to overlap between segments.
+    tol : float, optional
+        The allowed variance of a bin's weighted sum from the median bin
+        sum.
+
+    Returns
+    -------
+    verdict : bool
+        `True` if chosen combination satisfies COLA within `tol`,
+        `False` otherwise
+
+    See Also
+    --------
+    check_NOLA: Check whether the Nonzero Overlap Add (NOLA) constraint is met
+    stft: Short Time Fourier Transform
+    istft: Inverse Short Time Fourier Transform
+
+    Notes
+    -----
+    In order to enable inversion of an STFT via the inverse STFT in
+    `istft`, it is sufficient that the signal windowing obeys the constraint of
+    "Constant OverLap Add" (COLA). This ensures that every point in the input
+    data is equally weighted, thereby avoiding aliasing and allowing full
+    reconstruction.
+
+    Some examples of windows that satisfy COLA:
+        - Rectangular window at overlap of 0, 1/2, 2/3, 3/4, ...
+        - Bartlett window at overlap of 1/2, 3/4, 5/6, ...
+        - Hann window at 1/2, 2/3, 3/4, ...
+        - Any Blackman family window at 2/3 overlap
+        - Any window with ``noverlap = nperseg-1``
+
+    A very comprehensive list of other windows may be found in [2]_,
+    wherein the COLA condition is satisfied when the "Amplitude
+    Flatness" is unity.
+
+    .. versionadded:: 0.19.0
+
+    References
+    ----------
+    .. [1] Julius O. Smith III, "Spectral Audio Signal Processing", W3K
+           Publishing, 2011,ISBN 978-0-9745607-3-1.
+    .. [2] G. Heinzel, A. Ruediger and R. Schilling, "Spectrum and
+           spectral density estimation by the Discrete Fourier transform
+           (DFT), including a comprehensive list of window functions and
+           some new at-top windows", 2002,
+           http://hdl.handle.net/11858/00-001M-0000-0013-557A-5
+
+    Examples
+    --------
+    >>> from scipy import signal
+
+    Confirm COLA condition for rectangular window of 75% (3/4) overlap:
+
+    >>> signal.check_COLA(signal.windows.boxcar(100), 100, 75)
+    True
+
+    COLA is not true for 25% (1/4) overlap, though:
+
+    >>> signal.check_COLA(signal.windows.boxcar(100), 100, 25)
+    False
+
+    "Symmetrical" Hann window (for filter design) is not COLA:
+
+    >>> signal.check_COLA(signal.windows.hann(120, sym=True), 120, 60)
+    False
+
+    "Periodic" or "DFT-even" Hann window (for FFT analysis) is COLA for
+    overlap of 1/2, 2/3, 3/4, etc.:
+
+    >>> signal.check_COLA(signal.windows.hann(120, sym=False), 120, 60)
+    True
+
+    >>> signal.check_COLA(signal.windows.hann(120, sym=False), 120, 80)
+    True
+
+    >>> signal.check_COLA(signal.windows.hann(120, sym=False), 120, 90)
+    True
+
+    """
+    nperseg = int(nperseg)
+
+    if nperseg < 1:
+        raise ValueError('nperseg must be a positive integer')
+
+    if noverlap >= nperseg:
+        raise ValueError('noverlap must be less than nperseg.')
+    noverlap = int(noverlap)
+
+    if isinstance(window, str) or type(window) is tuple:
+        win = get_window(window, nperseg)
+    else:
+        win = np.asarray(window)
+        if len(win.shape) != 1:
+            raise ValueError('window must be 1-D')
+        if win.shape[0] != nperseg:
+            raise ValueError('window must have length of nperseg')
+
+    step = nperseg - noverlap
+    binsums = sum(win[ii*step:(ii+1)*step] for ii in range(nperseg//step))
+
+    if nperseg % step != 0:
+        binsums[:nperseg % step] += win[-(nperseg % step):]
+
+    deviation = binsums - np.median(binsums)
+    return np.max(np.abs(deviation)) < tol
+
+
+def check_NOLA(window, nperseg, noverlap, tol=1e-10):
+    r"""Check whether the Nonzero Overlap Add (NOLA) constraint is met.
+
+    Parameters
+    ----------
+    window : str or tuple or array_like
+        Desired window to use. If `window` is a string or tuple, it is
+        passed to `get_window` to generate the window values, which are
+        DFT-even by default. See `get_window` for a list of windows and
+        required parameters. If `window` is array_like it will be used
+        directly as the window and its length must be nperseg.
+    nperseg : int
+        Length of each segment.
+    noverlap : int
+        Number of points to overlap between segments.
+    tol : float, optional
+        The allowed variance of a bin's weighted sum from the median bin
+        sum.
+
+    Returns
+    -------
+    verdict : bool
+        `True` if chosen combination satisfies the NOLA constraint within
+        `tol`, `False` otherwise
+
+    See Also
+    --------
+    check_COLA: Check whether the Constant OverLap Add (COLA) constraint is met
+    stft: Short Time Fourier Transform
+    istft: Inverse Short Time Fourier Transform
+
+    Notes
+    -----
+    In order to enable inversion of an STFT via the inverse STFT in
+    `istft`, the signal windowing must obey the constraint of "nonzero
+    overlap add" (NOLA):
+
+    .. math:: \sum_{t}w^{2}[n-tH] \ne 0
+
+    for all :math:`n`, where :math:`w` is the window function, :math:`t` is the
+    frame index, and :math:`H` is the hop size (:math:`H` = `nperseg` -
+    `noverlap`).
+
+    This ensures that the normalization factors in the denominator of the
+    overlap-add inversion equation are not zero. Only very pathological windows
+    will fail the NOLA constraint.
+
+    .. versionadded:: 1.2.0
+
+    References
+    ----------
+    .. [1] Julius O. Smith III, "Spectral Audio Signal Processing", W3K
+           Publishing, 2011,ISBN 978-0-9745607-3-1.
+    .. [2] G. Heinzel, A. Ruediger and R. Schilling, "Spectrum and
+           spectral density estimation by the Discrete Fourier transform
+           (DFT), including a comprehensive list of window functions and
+           some new at-top windows", 2002,
+           http://hdl.handle.net/11858/00-001M-0000-0013-557A-5
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy import signal
+
+    Confirm NOLA condition for rectangular window of 75% (3/4) overlap:
+
+    >>> signal.check_NOLA(signal.windows.boxcar(100), 100, 75)
+    True
+
+    NOLA is also true for 25% (1/4) overlap:
+
+    >>> signal.check_NOLA(signal.windows.boxcar(100), 100, 25)
+    True
+
+    "Symmetrical" Hann window (for filter design) is also NOLA:
+
+    >>> signal.check_NOLA(signal.windows.hann(120, sym=True), 120, 60)
+    True
+
+    As long as there is overlap, it takes quite a pathological window to fail
+    NOLA:
+
+    >>> w = np.ones(64, dtype="float")
+    >>> w[::2] = 0
+    >>> signal.check_NOLA(w, 64, 32)
+    False
+
+    If there is not enough overlap, a window with zeros at the ends will not
+    work:
+
+    >>> signal.check_NOLA(signal.windows.hann(64), 64, 0)
+    False
+    >>> signal.check_NOLA(signal.windows.hann(64), 64, 1)
+    False
+    >>> signal.check_NOLA(signal.windows.hann(64), 64, 2)
+    True
+
+    """
+    nperseg = int(nperseg)
+
+    if nperseg < 1:
+        raise ValueError('nperseg must be a positive integer')
+
+    if noverlap >= nperseg:
+        raise ValueError('noverlap must be less than nperseg')
+    if noverlap < 0:
+        raise ValueError('noverlap must be a nonnegative integer')
+    noverlap = int(noverlap)
+
+    if isinstance(window, str) or type(window) is tuple:
+        win = get_window(window, nperseg)
+    else:
+        win = np.asarray(window)
+        if len(win.shape) != 1:
+            raise ValueError('window must be 1-D')
+        if win.shape[0] != nperseg:
+            raise ValueError('window must have length of nperseg')
+
+    step = nperseg - noverlap
+    binsums = sum(win[ii*step:(ii+1)*step]**2 for ii in range(nperseg//step))
+
+    if nperseg % step != 0:
+        binsums[:nperseg % step] += win[-(nperseg % step):]**2
+
+    return np.min(binsums) > tol
+
+
+def stft(x, fs=1.0, window='hann', nperseg=256, noverlap=None, nfft=None,
+         detrend=False, return_onesided=True, boundary='zeros', padded=True,
+         axis=-1, scaling='spectrum'):
+    r"""Compute the Short Time Fourier Transform (legacy function).
+
+    STFTs can be used as a way of quantifying the change of a
+    nonstationary signal's frequency and phase content over time.
+
+    .. legacy:: function
+
+        `ShortTimeFFT` is a newer STFT / ISTFT implementation with more
+        features. A :ref:`comparison <tutorial_stft_legacy_stft>` between the
+        implementations can be found in the :ref:`tutorial_stft` section of the
+        :ref:`user_guide`.
+
+    Parameters
+    ----------
+    x : array_like
+        Time series of measurement values
+    fs : float, optional
+        Sampling frequency of the `x` time series. Defaults to 1.0.
+    window : str or tuple or array_like, optional
+        Desired window to use. If `window` is a string or tuple, it is
+        passed to `get_window` to generate the window values, which are
+        DFT-even by default. See `get_window` for a list of windows and
+        required parameters. If `window` is array_like it will be used
+        directly as the window and its length must be nperseg. Defaults
+        to a Hann window.
+    nperseg : int, optional
+        Length of each segment. Defaults to 256.
+    noverlap : int, optional
+        Number of points to overlap between segments. If `None`,
+        ``noverlap = nperseg // 2``. Defaults to `None`. When
+        specified, the COLA constraint must be met (see Notes below).
+    nfft : int, optional
+        Length of the FFT used, if a zero padded FFT is desired. If
+        `None`, the FFT length is `nperseg`. Defaults to `None`.
+    detrend : str or function or `False`, optional
+        Specifies how to detrend each segment. If `detrend` is a
+        string, it is passed as the `type` argument to the `detrend`
+        function. If it is a function, it takes a segment and returns a
+        detrended segment. If `detrend` is `False`, no detrending is
+        done. Defaults to `False`.
+    return_onesided : bool, optional
+        If `True`, return a one-sided spectrum for real data. If
+        `False` return a two-sided spectrum. Defaults to `True`, but for
+        complex data, a two-sided spectrum is always returned.
+    boundary : str or None, optional
+        Specifies whether the input signal is extended at both ends, and
+        how to generate the new values, in order to center the first
+        windowed segment on the first input point. This has the benefit
+        of enabling reconstruction of the first input point when the
+        employed window function starts at zero. Valid options are
+        ``['even', 'odd', 'constant', 'zeros', None]``. Defaults to
+        'zeros', for zero padding extension. I.e. ``[1, 2, 3, 4]`` is
+        extended to ``[0, 1, 2, 3, 4, 0]`` for ``nperseg=3``.
+    padded : bool, optional
+        Specifies whether the input signal is zero-padded at the end to
+        make the signal fit exactly into an integer number of window
+        segments, so that all of the signal is included in the output.
+        Defaults to `True`. Padding occurs after boundary extension, if
+        `boundary` is not `None`, and `padded` is `True`, as is the
+        default.
+    axis : int, optional
+        Axis along which the STFT is computed; the default is over the
+        last axis (i.e. ``axis=-1``).
+    scaling: {'spectrum', 'psd'}
+        The default 'spectrum' scaling allows each frequency line of `Zxx` to
+        be interpreted as a magnitude spectrum. The 'psd' option scales each
+        line to a power spectral density - it allows to calculate the signal's
+        energy by numerically integrating over ``abs(Zxx)**2``.
+
+        .. versionadded:: 1.9.0
+
+    Returns
+    -------
+    f : ndarray
+        Array of sample frequencies.
+    t : ndarray
+        Array of segment times.
+    Zxx : ndarray
+        STFT of `x`. By default, the last axis of `Zxx` corresponds
+        to the segment times.
+
+    See Also
+    --------
+    istft: Inverse Short Time Fourier Transform
+    ShortTimeFFT: Newer STFT/ISTFT implementation providing more features.
+    check_COLA: Check whether the Constant OverLap Add (COLA) constraint
+                is met
+    check_NOLA: Check whether the Nonzero Overlap Add (NOLA) constraint is met
+    welch: Power spectral density by Welch's method.
+    spectrogram: Spectrogram by Welch's method.
+    csd: Cross spectral density by Welch's method.
+    lombscargle: Lomb-Scargle periodogram for unevenly sampled data
+
+    Notes
+    -----
+    In order to enable inversion of an STFT via the inverse STFT in
+    `istft`, the signal windowing must obey the constraint of "Nonzero
+    OverLap Add" (NOLA), and the input signal must have complete
+    windowing coverage (i.e. ``(x.shape[axis] - nperseg) %
+    (nperseg-noverlap) == 0``). The `padded` argument may be used to
+    accomplish this.
+
+    Given a time-domain signal :math:`x[n]`, a window :math:`w[n]`, and a hop
+    size :math:`H` = `nperseg - noverlap`, the windowed frame at time index
+    :math:`t` is given by
+
+    .. math:: x_{t}[n]=x[n]w[n-tH]
+
+    The overlap-add (OLA) reconstruction equation is given by
+
+    .. math:: x[n]=\frac{\sum_{t}x_{t}[n]w[n-tH]}{\sum_{t}w^{2}[n-tH]}
+
+    The NOLA constraint ensures that every normalization term that appears
+    in the denominator of the OLA reconstruction equation is nonzero. Whether a
+    choice of `window`, `nperseg`, and `noverlap` satisfy this constraint can
+    be tested with `check_NOLA`.
+
+
+    .. versionadded:: 0.19.0
+
+    References
+    ----------
+    .. [1] Oppenheim, Alan V., Ronald W. Schafer, John R. Buck
+           "Discrete-Time Signal Processing", Prentice Hall, 1999.
+    .. [2] Daniel W. Griffin, Jae S. Lim "Signal Estimation from
+           Modified Short-Time Fourier Transform", IEEE 1984,
+           10.1109/TASSP.1984.1164317
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> import matplotlib.pyplot as plt
+    >>> rng = np.random.default_rng()
+
+    Generate a test signal, a 2 Vrms sine wave whose frequency is slowly
+    modulated around 3kHz, corrupted by white noise of exponentially
+    decreasing magnitude sampled at 10 kHz.
+
+    >>> fs = 10e3
+    >>> N = 1e5
+    >>> amp = 2 * np.sqrt(2)
+    >>> noise_power = 0.01 * fs / 2
+    >>> time = np.arange(N) / float(fs)
+    >>> mod = 500*np.cos(2*np.pi*0.25*time)
+    >>> carrier = amp * np.sin(2*np.pi*3e3*time + mod)
+    >>> noise = rng.normal(scale=np.sqrt(noise_power),
+    ...                    size=time.shape)
+    >>> noise *= np.exp(-time/5)
+    >>> x = carrier + noise
+
+    Compute and plot the STFT's magnitude.
+
+    >>> f, t, Zxx = signal.stft(x, fs, nperseg=1000)
+    >>> plt.pcolormesh(t, f, np.abs(Zxx), vmin=0, vmax=amp, shading='gouraud')
+    >>> plt.title('STFT Magnitude')
+    >>> plt.ylabel('Frequency [Hz]')
+    >>> plt.xlabel('Time [sec]')
+    >>> plt.show()
+
+    Compare the energy of the signal `x` with the energy of its STFT:
+
+    >>> E_x = sum(x**2) / fs  # Energy of x
+    >>> # Calculate a two-sided STFT with PSD scaling:
+    >>> f, t, Zxx = signal.stft(x, fs, nperseg=1000, return_onesided=False,
+    ...                         scaling='psd')
+    >>> # Integrate numerically over abs(Zxx)**2:
+    >>> df, dt = f[1] - f[0], t[1] - t[0]
+    >>> E_Zxx = sum(np.sum(Zxx.real**2 + Zxx.imag**2, axis=0) * df) * dt
+    >>> # The energy is the same, but the numerical errors are quite large:
+    >>> np.isclose(E_x, E_Zxx, rtol=1e-2)
+    True
+
+    """
+    if scaling == 'psd':
+        scaling = 'density'
+    elif scaling != 'spectrum':
+        raise ValueError(f"Parameter {scaling=} not in ['spectrum', 'psd']!")
+
+    freqs, time, Zxx = _spectral_helper(x, x, fs, window, nperseg, noverlap,
+                                        nfft, detrend, return_onesided,
+                                        scaling=scaling, axis=axis,
+                                        mode='stft', boundary=boundary,
+                                        padded=padded)
+
+    return freqs, time, Zxx
+
+
+def istft(Zxx, fs=1.0, window='hann', nperseg=None, noverlap=None, nfft=None,
+          input_onesided=True, boundary=True, time_axis=-1, freq_axis=-2,
+          scaling='spectrum'):
+    r"""Perform the inverse Short Time Fourier transform (legacy function).
+
+    .. legacy:: function
+
+        `ShortTimeFFT` is a newer STFT / ISTFT implementation with more
+        features. A :ref:`comparison <tutorial_stft_legacy_stft>` between the
+        implementations can be found in the :ref:`tutorial_stft` section of the
+        :ref:`user_guide`.
+
+    Parameters
+    ----------
+    Zxx : array_like
+        STFT of the signal to be reconstructed. If a purely real array
+        is passed, it will be cast to a complex data type.
+    fs : float, optional
+        Sampling frequency of the time series. Defaults to 1.0.
+    window : str or tuple or array_like, optional
+        Desired window to use. If `window` is a string or tuple, it is
+        passed to `get_window` to generate the window values, which are
+        DFT-even by default. See `get_window` for a list of windows and
+        required parameters. If `window` is array_like it will be used
+        directly as the window and its length must be nperseg. Defaults
+        to a Hann window. Must match the window used to generate the
+        STFT for faithful inversion.
+    nperseg : int, optional
+        Number of data points corresponding to each STFT segment. This
+        parameter must be specified if the number of data points per
+        segment is odd, or if the STFT was padded via ``nfft >
+        nperseg``. If `None`, the value depends on the shape of
+        `Zxx` and `input_onesided`. If `input_onesided` is `True`,
+        ``nperseg=2*(Zxx.shape[freq_axis] - 1)``. Otherwise,
+        ``nperseg=Zxx.shape[freq_axis]``. Defaults to `None`.
+    noverlap : int, optional
+        Number of points to overlap between segments. If `None`, half
+        of the segment length. Defaults to `None`. When specified, the
+        COLA constraint must be met (see Notes below), and should match
+        the parameter used to generate the STFT. Defaults to `None`.
+    nfft : int, optional
+        Number of FFT points corresponding to each STFT segment. This
+        parameter must be specified if the STFT was padded via ``nfft >
+        nperseg``. If `None`, the default values are the same as for
+        `nperseg`, detailed above, with one exception: if
+        `input_onesided` is True and
+        ``nperseg==2*Zxx.shape[freq_axis] - 1``, `nfft` also takes on
+        that value. This case allows the proper inversion of an
+        odd-length unpadded STFT using ``nfft=None``. Defaults to
+        `None`.
+    input_onesided : bool, optional
+        If `True`, interpret the input array as one-sided FFTs, such
+        as is returned by `stft` with ``return_onesided=True`` and
+        `numpy.fft.rfft`. If `False`, interpret the input as a a
+        two-sided FFT. Defaults to `True`.
+    boundary : bool, optional
+        Specifies whether the input signal was extended at its
+        boundaries by supplying a non-`None` ``boundary`` argument to
+        `stft`. Defaults to `True`.
+    time_axis : int, optional
+        Where the time segments of the STFT is located; the default is
+        the last axis (i.e. ``axis=-1``).
+    freq_axis : int, optional
+        Where the frequency axis of the STFT is located; the default is
+        the penultimate axis (i.e. ``axis=-2``).
+    scaling: {'spectrum', 'psd'}
+        The default 'spectrum' scaling allows each frequency line of `Zxx` to
+        be interpreted as a magnitude spectrum. The 'psd' option scales each
+        line to a power spectral density - it allows to calculate the signal's
+        energy by numerically integrating over ``abs(Zxx)**2``.
+
+    Returns
+    -------
+    t : ndarray
+        Array of output data times.
+    x : ndarray
+        iSTFT of `Zxx`.
+
+    See Also
+    --------
+    stft: Short Time Fourier Transform
+    ShortTimeFFT: Newer STFT/ISTFT implementation providing more features.
+    check_COLA: Check whether the Constant OverLap Add (COLA) constraint
+                is met
+    check_NOLA: Check whether the Nonzero Overlap Add (NOLA) constraint is met
+
+    Notes
+    -----
+    In order to enable inversion of an STFT via the inverse STFT with
+    `istft`, the signal windowing must obey the constraint of "nonzero
+    overlap add" (NOLA):
+
+    .. math:: \sum_{t}w^{2}[n-tH] \ne 0
+
+    This ensures that the normalization factors that appear in the denominator
+    of the overlap-add reconstruction equation
+
+    .. math:: x[n]=\frac{\sum_{t}x_{t}[n]w[n-tH]}{\sum_{t}w^{2}[n-tH]}
+
+    are not zero. The NOLA constraint can be checked with the `check_NOLA`
+    function.
+
+    An STFT which has been modified (via masking or otherwise) is not
+    guaranteed to correspond to a exactly realizible signal. This
+    function implements the iSTFT via the least-squares estimation
+    algorithm detailed in [2]_, which produces a signal that minimizes
+    the mean squared error between the STFT of the returned signal and
+    the modified STFT.
+
+
+    .. versionadded:: 0.19.0
+
+    References
+    ----------
+    .. [1] Oppenheim, Alan V., Ronald W. Schafer, John R. Buck
+           "Discrete-Time Signal Processing", Prentice Hall, 1999.
+    .. [2] Daniel W. Griffin, Jae S. Lim "Signal Estimation from
+           Modified Short-Time Fourier Transform", IEEE 1984,
+           10.1109/TASSP.1984.1164317
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> import matplotlib.pyplot as plt
+    >>> rng = np.random.default_rng()
+
+    Generate a test signal, a 2 Vrms sine wave at 50Hz corrupted by
+    0.001 V**2/Hz of white noise sampled at 1024 Hz.
+
+    >>> fs = 1024
+    >>> N = 10*fs
+    >>> nperseg = 512
+    >>> amp = 2 * np.sqrt(2)
+    >>> noise_power = 0.001 * fs / 2
+    >>> time = np.arange(N) / float(fs)
+    >>> carrier = amp * np.sin(2*np.pi*50*time)
+    >>> noise = rng.normal(scale=np.sqrt(noise_power),
+    ...                    size=time.shape)
+    >>> x = carrier + noise
+
+    Compute the STFT, and plot its magnitude
+
+    >>> f, t, Zxx = signal.stft(x, fs=fs, nperseg=nperseg)
+    >>> plt.figure()
+    >>> plt.pcolormesh(t, f, np.abs(Zxx), vmin=0, vmax=amp, shading='gouraud')
+    >>> plt.ylim([f[1], f[-1]])
+    >>> plt.title('STFT Magnitude')
+    >>> plt.ylabel('Frequency [Hz]')
+    >>> plt.xlabel('Time [sec]')
+    >>> plt.yscale('log')
+    >>> plt.show()
+
+    Zero the components that are 10% or less of the carrier magnitude,
+    then convert back to a time series via inverse STFT
+
+    >>> Zxx = np.where(np.abs(Zxx) >= amp/10, Zxx, 0)
+    >>> _, xrec = signal.istft(Zxx, fs)
+
+    Compare the cleaned signal with the original and true carrier signals.
+
+    >>> plt.figure()
+    >>> plt.plot(time, x, time, xrec, time, carrier)
+    >>> plt.xlim([2, 2.1])
+    >>> plt.xlabel('Time [sec]')
+    >>> plt.ylabel('Signal')
+    >>> plt.legend(['Carrier + Noise', 'Filtered via STFT', 'True Carrier'])
+    >>> plt.show()
+
+    Note that the cleaned signal does not start as abruptly as the original,
+    since some of the coefficients of the transient were also removed:
+
+    >>> plt.figure()
+    >>> plt.plot(time, x, time, xrec, time, carrier)
+    >>> plt.xlim([0, 0.1])
+    >>> plt.xlabel('Time [sec]')
+    >>> plt.ylabel('Signal')
+    >>> plt.legend(['Carrier + Noise', 'Filtered via STFT', 'True Carrier'])
+    >>> plt.show()
+
+    """
+    # Make sure input is an ndarray of appropriate complex dtype
+    Zxx = np.asarray(Zxx) + 0j
+    freq_axis = int(freq_axis)
+    time_axis = int(time_axis)
+
+    if Zxx.ndim < 2:
+        raise ValueError('Input stft must be at least 2d!')
+
+    if freq_axis == time_axis:
+        raise ValueError('Must specify differing time and frequency axes!')
+
+    nseg = Zxx.shape[time_axis]
+
+    if input_onesided:
+        # Assume even segment length
+        n_default = 2*(Zxx.shape[freq_axis] - 1)
+    else:
+        n_default = Zxx.shape[freq_axis]
+
+    # Check windowing parameters
+    if nperseg is None:
+        nperseg = n_default
+    else:
+        nperseg = int(nperseg)
+        if nperseg < 1:
+            raise ValueError('nperseg must be a positive integer')
+
+    if nfft is None:
+        if (input_onesided) and (nperseg == n_default + 1):
+            # Odd nperseg, no FFT padding
+            nfft = nperseg
+        else:
+            nfft = n_default
+    elif nfft < nperseg:
+        raise ValueError('nfft must be greater than or equal to nperseg.')
+    else:
+        nfft = int(nfft)
+
+    if noverlap is None:
+        noverlap = nperseg//2
+    else:
+        noverlap = int(noverlap)
+    if noverlap >= nperseg:
+        raise ValueError('noverlap must be less than nperseg.')
+    nstep = nperseg - noverlap
+
+    # Rearrange axes if necessary
+    if time_axis != Zxx.ndim-1 or freq_axis != Zxx.ndim-2:
+        # Turn negative indices to positive for the call to transpose
+        if freq_axis < 0:
+            freq_axis = Zxx.ndim + freq_axis
+        if time_axis < 0:
+            time_axis = Zxx.ndim + time_axis
+        zouter = list(range(Zxx.ndim))
+        for ax in sorted([time_axis, freq_axis], reverse=True):
+            zouter.pop(ax)
+        Zxx = np.transpose(Zxx, zouter+[freq_axis, time_axis])
+
+    # Get window as array
+    if isinstance(window, str) or type(window) is tuple:
+        win = get_window(window, nperseg)
+    else:
+        win = np.asarray(window)
+        if len(win.shape) != 1:
+            raise ValueError('window must be 1-D')
+        if win.shape[0] != nperseg:
+            raise ValueError(f'window must have length of {nperseg}')
+
+    ifunc = sp_fft.irfft if input_onesided else sp_fft.ifft
+    xsubs = ifunc(Zxx, axis=-2, n=nfft)[..., :nperseg, :]
+
+    # Initialize output and normalization arrays
+    outputlength = nperseg + (nseg-1)*nstep
+    x = np.zeros(list(Zxx.shape[:-2])+[outputlength], dtype=xsubs.dtype)
+    norm = np.zeros(outputlength, dtype=xsubs.dtype)
+
+    if np.result_type(win, xsubs) != xsubs.dtype:
+        win = win.astype(xsubs.dtype)
+
+    if scaling == 'spectrum':
+        xsubs *= win.sum()
+    elif scaling == 'psd':
+        xsubs *= np.sqrt(fs * sum(win**2))
+    else:
+        raise ValueError(f"Parameter {scaling=} not in ['spectrum', 'psd']!")
+
+    # Construct the output from the ifft segments
+    # This loop could perhaps be vectorized/strided somehow...
+    for ii in range(nseg):
+        # Window the ifft
+        x[..., ii*nstep:ii*nstep+nperseg] += xsubs[..., ii] * win
+        norm[..., ii*nstep:ii*nstep+nperseg] += win**2
+
+    # Remove extension points
+    if boundary:
+        x = x[..., nperseg//2:-(nperseg//2)]
+        norm = norm[..., nperseg//2:-(nperseg//2)]
+
+    # Divide out normalization where non-tiny
+    if np.sum(norm > 1e-10) != len(norm):
+        warnings.warn(
+            "NOLA condition failed, STFT may not be invertible."
+            + (" Possibly due to missing boundary" if not boundary else ""),
+            stacklevel=2
+        )
+    x /= np.where(norm > 1e-10, norm, 1.0)
+
+    if input_onesided:
+        x = x.real
+
+    # Put axes back
+    if x.ndim > 1:
+        if time_axis != Zxx.ndim-1:
+            if freq_axis < time_axis:
+                time_axis -= 1
+            x = np.moveaxis(x, -1, time_axis)
+
+    time = np.arange(x.shape[0])/float(fs)
+    return time, x
+
+
+def coherence(x, y, fs=1.0, window='hann', nperseg=None, noverlap=None,
+              nfft=None, detrend='constant', axis=-1):
+    r"""
+    Estimate the magnitude squared coherence estimate, Cxy, of
+    discrete-time signals X and Y using Welch's method.
+
+    ``Cxy = abs(Pxy)**2/(Pxx*Pyy)``, where `Pxx` and `Pyy` are power
+    spectral density estimates of X and Y, and `Pxy` is the cross
+    spectral density estimate of X and Y.
+
+    Parameters
+    ----------
+    x : array_like
+        Time series of measurement values
+    y : array_like
+        Time series of measurement values
+    fs : float, optional
+        Sampling frequency of the `x` and `y` time series. Defaults
+        to 1.0.
+    window : str or tuple or array_like, optional
+        Desired window to use. If `window` is a string or tuple, it is
+        passed to `get_window` to generate the window values, which are
+        DFT-even by default. See `get_window` for a list of windows and
+        required parameters. If `window` is array_like it will be used
+        directly as the window and its length must be nperseg. Defaults
+        to a Hann window.
+    nperseg : int, optional
+        Length of each segment. Defaults to None, but if window is str or
+        tuple, is set to 256, and if window is array_like, is set to the
+        length of the window.
+    noverlap: int, optional
+        Number of points to overlap between segments. If `None`,
+        ``noverlap = nperseg // 2``. Defaults to `None`.
+    nfft : int, optional
+        Length of the FFT used, if a zero padded FFT is desired. If
+        `None`, the FFT length is `nperseg`. Defaults to `None`.
+    detrend : str or function or `False`, optional
+        Specifies how to detrend each segment. If `detrend` is a
+        string, it is passed as the `type` argument to the `detrend`
+        function. If it is a function, it takes a segment and returns a
+        detrended segment. If `detrend` is `False`, no detrending is
+        done. Defaults to 'constant'.
+    axis : int, optional
+        Axis along which the coherence is computed for both inputs; the
+        default is over the last axis (i.e. ``axis=-1``).
+
+    Returns
+    -------
+    f : ndarray
+        Array of sample frequencies.
+    Cxy : ndarray
+        Magnitude squared coherence of x and y.
+
+    See Also
+    --------
+    periodogram: Simple, optionally modified periodogram
+    lombscargle: Lomb-Scargle periodogram for unevenly sampled data
+    welch: Power spectral density by Welch's method.
+    csd: Cross spectral density by Welch's method.
+
+    Notes
+    -----
+    An appropriate amount of overlap will depend on the choice of window
+    and on your requirements. For the default Hann window an overlap of
+    50% is a reasonable trade off between accurately estimating the
+    signal power, while not over counting any of the data. Narrower
+    windows may require a larger overlap.
+
+    .. versionadded:: 0.16.0
+
+    References
+    ----------
+    .. [1] P. Welch, "The use of the fast Fourier transform for the
+           estimation of power spectra: A method based on time averaging
+           over short, modified periodograms", IEEE Trans. Audio
+           Electroacoust. vol. 15, pp. 70-73, 1967.
+    .. [2] Stoica, Petre, and Randolph Moses, "Spectral Analysis of
+           Signals" Prentice Hall, 2005
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> import matplotlib.pyplot as plt
+    >>> rng = np.random.default_rng()
+
+    Generate two test signals with some common features.
+
+    >>> fs = 10e3
+    >>> N = 1e5
+    >>> amp = 20
+    >>> freq = 1234.0
+    >>> noise_power = 0.001 * fs / 2
+    >>> time = np.arange(N) / fs
+    >>> b, a = signal.butter(2, 0.25, 'low')
+    >>> x = rng.normal(scale=np.sqrt(noise_power), size=time.shape)
+    >>> y = signal.lfilter(b, a, x)
+    >>> x += amp*np.sin(2*np.pi*freq*time)
+    >>> y += rng.normal(scale=0.1*np.sqrt(noise_power), size=time.shape)
+
+    Compute and plot the coherence.
+
+    >>> f, Cxy = signal.coherence(x, y, fs, nperseg=1024)
+    >>> plt.semilogy(f, Cxy)
+    >>> plt.xlabel('frequency [Hz]')
+    >>> plt.ylabel('Coherence')
+    >>> plt.show()
+
+    """
+    freqs, Pxx = welch(x, fs=fs, window=window, nperseg=nperseg,
+                       noverlap=noverlap, nfft=nfft, detrend=detrend,
+                       axis=axis)
+    _, Pyy = welch(y, fs=fs, window=window, nperseg=nperseg, noverlap=noverlap,
+                   nfft=nfft, detrend=detrend, axis=axis)
+    _, Pxy = csd(x, y, fs=fs, window=window, nperseg=nperseg,
+                 noverlap=noverlap, nfft=nfft, detrend=detrend, axis=axis)
+
+    Cxy = np.abs(Pxy)**2 / Pxx / Pyy
+
+    return freqs, Cxy
+
+
+def _spectral_helper(x, y, fs=1.0, window='hann', nperseg=None, noverlap=None,
+                     nfft=None, detrend='constant', return_onesided=True,
+                     scaling='density', axis=-1, mode='psd', boundary=None,
+                     padded=False):
+    """Calculate various forms of windowed FFTs for PSD, CSD, etc.
+
+    This is a helper function that implements the commonality between
+    the stft, psd, csd, and spectrogram functions. It is not designed to
+    be called externally. The windows are not averaged over; the result
+    from each window is returned.
+
+    Parameters
+    ----------
+    x : array_like
+        Array or sequence containing the data to be analyzed.
+    y : array_like
+        Array or sequence containing the data to be analyzed. If this is
+        the same object in memory as `x` (i.e. ``_spectral_helper(x,
+        x, ...)``), the extra computations are spared.
+    fs : float, optional
+        Sampling frequency of the time series. Defaults to 1.0.
+    window : str or tuple or array_like, optional
+        Desired window to use. If `window` is a string or tuple, it is
+        passed to `get_window` to generate the window values, which are
+        DFT-even by default. See `get_window` for a list of windows and
+        required parameters. If `window` is array_like it will be used
+        directly as the window and its length must be nperseg. Defaults
+        to a Hann window.
+    nperseg : int, optional
+        Length of each segment. Defaults to None, but if window is str or
+        tuple, is set to 256, and if window is array_like, is set to the
+        length of the window.
+    noverlap : int, optional
+        Number of points to overlap between segments. If `None`,
+        ``noverlap = nperseg // 2``. Defaults to `None`.
+    nfft : int, optional
+        Length of the FFT used, if a zero padded FFT is desired. If
+        `None`, the FFT length is `nperseg`. Defaults to `None`.
+    detrend : str or function or `False`, optional
+        Specifies how to detrend each segment. If `detrend` is a
+        string, it is passed as the `type` argument to the `detrend`
+        function. If it is a function, it takes a segment and returns a
+        detrended segment. If `detrend` is `False`, no detrending is
+        done. Defaults to 'constant'.
+    return_onesided : bool, optional
+        If `True`, return a one-sided spectrum for real data. If
+        `False` return a two-sided spectrum. Defaults to `True`, but for
+        complex data, a two-sided spectrum is always returned.
+    scaling : { 'density', 'spectrum' }, optional
+        Selects between computing the cross spectral density ('density')
+        where `Pxy` has units of V**2/Hz and computing the cross
+        spectrum ('spectrum') where `Pxy` has units of V**2, if `x`
+        and `y` are measured in V and `fs` is measured in Hz.
+        Defaults to 'density'
+    axis : int, optional
+        Axis along which the FFTs are computed; the default is over the
+        last axis (i.e. ``axis=-1``).
+    mode: str {'psd', 'stft'}, optional
+        Defines what kind of return values are expected. Defaults to
+        'psd'.
+    boundary : str or None, optional
+        Specifies whether the input signal is extended at both ends, and
+        how to generate the new values, in order to center the first
+        windowed segment on the first input point. This has the benefit
+        of enabling reconstruction of the first input point when the
+        employed window function starts at zero. Valid options are
+        ``['even', 'odd', 'constant', 'zeros', None]``. Defaults to
+        `None`.
+    padded : bool, optional
+        Specifies whether the input signal is zero-padded at the end to
+        make the signal fit exactly into an integer number of window
+        segments, so that all of the signal is included in the output.
+        Defaults to `False`. Padding occurs after boundary extension, if
+        `boundary` is not `None`, and `padded` is `True`.
+
+    Returns
+    -------
+    freqs : ndarray
+        Array of sample frequencies.
+    t : ndarray
+        Array of times corresponding to each data segment
+    result : ndarray
+        Array of output data, contents dependent on *mode* kwarg.
+
+    Notes
+    -----
+    Adapted from matplotlib.mlab
+
+    .. versionadded:: 0.16.0
+    """
+    if mode not in ['psd', 'stft']:
+        raise ValueError(f"Unknown value for mode {mode}, must be one of: "
+                         "{'psd', 'stft'}")
+
+    boundary_funcs = {'even': even_ext,
+                      'odd': odd_ext,
+                      'constant': const_ext,
+                      'zeros': zero_ext,
+                      None: None}
+
+    if boundary not in boundary_funcs:
+        raise ValueError(f"Unknown boundary option '{boundary}', "
+                         f"must be one of: {list(boundary_funcs.keys())}")
+
+    # If x and y are the same object we can save ourselves some computation.
+    same_data = y is x
+
+    if not same_data and mode != 'psd':
+        raise ValueError("x and y must be equal if mode is 'stft'")
+
+    axis = int(axis)
+
+    # Ensure we have np.arrays, get outdtype
+    x = np.asarray(x)
+    if not same_data:
+        y = np.asarray(y)
+        outdtype = np.result_type(x, y, np.complex64)
+    else:
+        outdtype = np.result_type(x, np.complex64)
+
+    if not same_data:
+        # Check if we can broadcast the outer axes together
+        xouter = list(x.shape)
+        youter = list(y.shape)
+        xouter.pop(axis)
+        youter.pop(axis)
+        try:
+            outershape = np.broadcast(np.empty(xouter), np.empty(youter)).shape
+        except ValueError as e:
+            raise ValueError('x and y cannot be broadcast together.') from e
+
+    if same_data:
+        if x.size == 0:
+            return np.empty(x.shape), np.empty(x.shape), np.empty(x.shape)
+    else:
+        if x.size == 0 or y.size == 0:
+            outshape = outershape + (min([x.shape[axis], y.shape[axis]]),)
+            emptyout = np.moveaxis(np.empty(outshape), -1, axis)
+            return emptyout, emptyout, emptyout
+
+    if x.ndim > 1:
+        if axis != -1:
+            x = np.moveaxis(x, axis, -1)
+            if not same_data and y.ndim > 1:
+                y = np.moveaxis(y, axis, -1)
+
+    # Check if x and y are the same length, zero-pad if necessary
+    if not same_data:
+        if x.shape[-1] != y.shape[-1]:
+            if x.shape[-1] < y.shape[-1]:
+                pad_shape = list(x.shape)
+                pad_shape[-1] = y.shape[-1] - x.shape[-1]
+                x = np.concatenate((x, np.zeros(pad_shape)), -1)
+            else:
+                pad_shape = list(y.shape)
+                pad_shape[-1] = x.shape[-1] - y.shape[-1]
+                y = np.concatenate((y, np.zeros(pad_shape)), -1)
+
+    if nperseg is not None:  # if specified by user
+        nperseg = int(nperseg)
+        if nperseg < 1:
+            raise ValueError('nperseg must be a positive integer')
+
+    # parse window; if array like, then set nperseg = win.shape
+    win, nperseg = _triage_segments(window, nperseg, input_length=x.shape[-1])
+
+    if nfft is None:
+        nfft = nperseg
+    elif nfft < nperseg:
+        raise ValueError('nfft must be greater than or equal to nperseg.')
+    else:
+        nfft = int(nfft)
+
+    if noverlap is None:
+        noverlap = nperseg//2
+    else:
+        noverlap = int(noverlap)
+    if noverlap >= nperseg:
+        raise ValueError('noverlap must be less than nperseg.')
+    nstep = nperseg - noverlap
+
+    # Padding occurs after boundary extension, so that the extended signal ends
+    # in zeros, instead of introducing an impulse at the end.
+    # I.e. if x = [..., 3, 2]
+    # extend then pad -> [..., 3, 2, 2, 3, 0, 0, 0]
+    # pad then extend -> [..., 3, 2, 0, 0, 0, 2, 3]
+
+    if boundary is not None:
+        ext_func = boundary_funcs[boundary]
+        x = ext_func(x, nperseg//2, axis=-1)
+        if not same_data:
+            y = ext_func(y, nperseg//2, axis=-1)
+
+    if padded:
+        # Pad to integer number of windowed segments
+        # I.e. make x.shape[-1] = nperseg + (nseg-1)*nstep, with integer nseg
+        nadd = (-(x.shape[-1]-nperseg) % nstep) % nperseg
+        zeros_shape = list(x.shape[:-1]) + [nadd]
+        x = np.concatenate((x, np.zeros(zeros_shape)), axis=-1)
+        if not same_data:
+            zeros_shape = list(y.shape[:-1]) + [nadd]
+            y = np.concatenate((y, np.zeros(zeros_shape)), axis=-1)
+
+    # Handle detrending and window functions
+    if not detrend:
+        def detrend_func(d):
+            return d
+    elif not hasattr(detrend, '__call__'):
+        def detrend_func(d):
+            return _signaltools.detrend(d, type=detrend, axis=-1)
+    elif axis != -1:
+        # Wrap this function so that it receives a shape that it could
+        # reasonably expect to receive.
+        def detrend_func(d):
+            d = np.moveaxis(d, -1, axis)
+            d = detrend(d)
+            return np.moveaxis(d, axis, -1)
+    else:
+        detrend_func = detrend
+
+    if np.result_type(win, np.complex64) != outdtype:
+        win = win.astype(outdtype)
+
+    if scaling == 'density':
+        scale = 1.0 / (fs * (win*win).sum())
+    elif scaling == 'spectrum':
+        scale = 1.0 / win.sum()**2
+    else:
+        raise ValueError(f'Unknown scaling: {scaling!r}')
+
+    if mode == 'stft':
+        scale = np.sqrt(scale)
+
+    if return_onesided:
+        if np.iscomplexobj(x):
+            sides = 'twosided'
+            warnings.warn('Input data is complex, switching to return_onesided=False',
+                          stacklevel=3)
+        else:
+            sides = 'onesided'
+            if not same_data:
+                if np.iscomplexobj(y):
+                    sides = 'twosided'
+                    warnings.warn('Input data is complex, switching to '
+                                  'return_onesided=False',
+                                  stacklevel=3)
+    else:
+        sides = 'twosided'
+
+    if sides == 'twosided':
+        freqs = sp_fft.fftfreq(nfft, 1/fs)
+    elif sides == 'onesided':
+        freqs = sp_fft.rfftfreq(nfft, 1/fs)
+
+    # Perform the windowed FFTs
+    result = _fft_helper(x, win, detrend_func, nperseg, noverlap, nfft, sides)
+
+    if not same_data:
+        # All the same operations on the y data
+        result_y = _fft_helper(y, win, detrend_func, nperseg, noverlap, nfft,
+                               sides)
+        result = np.conjugate(result) * result_y
+    elif mode == 'psd':
+        result = np.conjugate(result) * result
+
+    result *= scale
+    if sides == 'onesided' and mode == 'psd':
+        if nfft % 2:
+            result[..., 1:] *= 2
+        else:
+            # Last point is unpaired Nyquist freq point, don't double
+            result[..., 1:-1] *= 2
+
+    time = np.arange(nperseg/2, x.shape[-1] - nperseg/2 + 1,
+                     nperseg - noverlap)/float(fs)
+    if boundary is not None:
+        time -= (nperseg/2) / fs
+
+    result = result.astype(outdtype)
+
+    # All imaginary parts are zero anyways
+    if same_data and mode != 'stft':
+        result = result.real
+
+    # Output is going to have new last axis for time/window index, so a
+    # negative axis index shifts down one
+    if axis < 0:
+        axis -= 1
+
+    # Roll frequency axis back to axis where the data came from
+    result = np.moveaxis(result, -1, axis)
+
+    return freqs, time, result
+
+
+def _fft_helper(x, win, detrend_func, nperseg, noverlap, nfft, sides):
+    """
+    Calculate windowed FFT, for internal use by
+    `scipy.signal._spectral_helper`.
+
+    This is a helper function that does the main FFT calculation for
+    `_spectral helper`. All input validation is performed there, and the
+    data axis is assumed to be the last axis of x. It is not designed to
+    be called externally. The windows are not averaged over; the result
+    from each window is returned.
+
+    Returns
+    -------
+    result : ndarray
+        Array of FFT data
+
+    Notes
+    -----
+    Adapted from matplotlib.mlab
+
+    .. versionadded:: 0.16.0
+    """
+    # Created sliding window view of array
+    if nperseg == 1 and noverlap == 0:
+        result = x[..., np.newaxis]
+    else:
+        step = nperseg - noverlap
+        result = np.lib.stride_tricks.sliding_window_view(
+            x, window_shape=nperseg, axis=-1, writeable=True
+        )
+        result = result[..., 0::step, :]
+
+    # Detrend each data segment individually
+    result = detrend_func(result)
+
+    # Apply window by multiplication
+    result = win * result
+
+    # Perform the fft. Acts on last axis by default. Zero-pads automatically
+    if sides == 'twosided':
+        func = sp_fft.fft
+    else:
+        result = result.real
+        func = sp_fft.rfft
+    result = func(result, n=nfft)
+
+    return result
+
+
+def _triage_segments(window, nperseg, input_length):
+    """
+    Parses window and nperseg arguments for spectrogram and _spectral_helper.
+    This is a helper function, not meant to be called externally.
+
+    Parameters
+    ----------
+    window : string, tuple, or ndarray
+        If window is specified by a string or tuple and nperseg is not
+        specified, nperseg is set to the default of 256 and returns a window of
+        that length.
+        If instead the window is array_like and nperseg is not specified, then
+        nperseg is set to the length of the window. A ValueError is raised if
+        the user supplies both an array_like window and a value for nperseg but
+        nperseg does not equal the length of the window.
+
+    nperseg : int
+        Length of each segment
+
+    input_length: int
+        Length of input signal, i.e. x.shape[-1]. Used to test for errors.
+
+    Returns
+    -------
+    win : ndarray
+        window. If function was called with string or tuple than this will hold
+        the actual array used as a window.
+
+    nperseg : int
+        Length of each segment. If window is str or tuple, nperseg is set to
+        256. If window is array_like, nperseg is set to the length of the
+        window.
+    """
+    # parse window; if array like, then set nperseg = win.shape
+    if isinstance(window, str) or isinstance(window, tuple):
+        # if nperseg not specified
+        if nperseg is None:
+            nperseg = 256  # then change to default
+        if nperseg > input_length:
+            warnings.warn(f'nperseg = {nperseg:d} is greater than input length '
+                          f' = {input_length:d}, using nperseg = {input_length:d}',
+                          stacklevel=3)
+            nperseg = input_length
+        win = get_window(window, nperseg)
+    else:
+        win = np.asarray(window)
+        if len(win.shape) != 1:
+            raise ValueError('window must be 1-D')
+        if input_length < win.shape[-1]:
+            raise ValueError('window is longer than input signal')
+        if nperseg is None:
+            nperseg = win.shape[0]
+        elif nperseg is not None:
+            if nperseg != win.shape[0]:
+                raise ValueError("value specified for nperseg is different"
+                                 " from length of window")
+    return win, nperseg
+
+
+def _median_bias(n):
+    """
+    Returns the bias of the median of a set of periodograms relative to
+    the mean.
+
+    See Appendix B from [1]_ for details.
+
+    Parameters
+    ----------
+    n : int
+        Numbers of periodograms being averaged.
+
+    Returns
+    -------
+    bias : float
+        Calculated bias.
+
+    References
+    ----------
+    .. [1] B. Allen, W.G. Anderson, P.R. Brady, D.A. Brown, J.D.E. Creighton.
+           "FINDCHIRP: an algorithm for detection of gravitational waves from
+           inspiraling compact binaries", Physical Review D 85, 2012,
+           :arxiv:`gr-qc/0509116`
+    """
+    ii_2 = 2 * np.arange(1., (n-1) // 2 + 1)
+    return 1 + np.sum(1. / (ii_2 + 1) - 1. / ii_2)

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_spline.pyi

@@ -0,0 +1,34 @@
+
+import numpy as np
+from numpy.typing import NDArray
+
+FloatingArray = NDArray[np.float32] | NDArray[np.float64]
+ComplexArray = NDArray[np.complex64] | NDArray[np.complex128]
+FloatingComplexArray = FloatingArray | ComplexArray
+
+
+def symiirorder1_ic(signal: FloatingComplexArray,
+                    c0: float,
+                    z1: float,
+                    precision: float) -> FloatingComplexArray:
+    ...
+
+
+def symiirorder2_ic_fwd(signal: FloatingArray,
+                        r: float,
+                        omega: float,
+                        precision: float) -> FloatingArray:
+    ...
+
+
+def symiirorder2_ic_bwd(signal: FloatingArray,
+                        r: float,
+                        omega: float,
+                        precision: float) -> FloatingArray:
+    ...
+
+
+def sepfir2d(input: FloatingComplexArray,
+             hrow: FloatingComplexArray,
+             hcol: FloatingComplexArray) -> FloatingComplexArray:
+    ...

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_spline_filters.py

@@ -0,0 +1,808 @@
+from numpy import (asarray, pi, zeros_like,
+                   array, arctan2, tan, ones, arange, floor,
+                   r_, atleast_1d, sqrt, exp, greater, cos, add, sin,
+                   moveaxis, abs, arctan, complex64, float32)
+import numpy as np
+
+from scipy._lib._util import normalize_axis_index
+
+# From splinemodule.c
+from ._spline import sepfir2d, symiirorder1_ic, symiirorder2_ic_fwd, symiirorder2_ic_bwd
+from ._signaltools import lfilter, sosfilt, lfiltic
+from ._arraytools import axis_slice, axis_reverse
+
+from scipy.interpolate import BSpline
+
+
+__all__ = ['spline_filter', 'gauss_spline',
+           'cspline1d', 'qspline1d', 'qspline2d', 'cspline2d',
+           'cspline1d_eval', 'qspline1d_eval', 'symiirorder1', 'symiirorder2']
+
+
+def spline_filter(Iin, lmbda=5.0):
+    """Smoothing spline (cubic) filtering of a rank-2 array.
+
+    Filter an input data set, `Iin`, using a (cubic) smoothing spline of
+    fall-off `lmbda`.
+
+    Parameters
+    ----------
+    Iin : array_like
+        input data set
+    lmbda : float, optional
+        spline smoothing fall-off value, default is `5.0`.
+
+    Returns
+    -------
+    res : ndarray
+        filtered input data
+
+    Examples
+    --------
+    We can filter an multi dimensional signal (ex: 2D image) using cubic
+    B-spline filter:
+
+    >>> import numpy as np
+    >>> from scipy.signal import spline_filter
+    >>> import matplotlib.pyplot as plt
+    >>> orig_img = np.eye(20)  # create an image
+    >>> orig_img[10, :] = 1.0
+    >>> sp_filter = spline_filter(orig_img, lmbda=0.1)
+    >>> f, ax = plt.subplots(1, 2, sharex=True)
+    >>> for ind, data in enumerate([[orig_img, "original image"],
+    ...                             [sp_filter, "spline filter"]]):
+    ...     ax[ind].imshow(data[0], cmap='gray_r')
+    ...     ax[ind].set_title(data[1])
+    >>> plt.tight_layout()
+    >>> plt.show()
+
+    """
+    if Iin.dtype not in [np.float32, np.float64, np.complex64, np.complex128]:
+        raise TypeError(f"Invalid data type for Iin: {Iin.dtype = }")
+
+    # XXX: note that complex-valued computations are done in single precision
+    # this is historic, and the root reason is unclear,
+    # see https://github.com/scipy/scipy/issues/9209
+    # Attempting to work in complex double precision leads to symiirorder1
+    # failing to converge for the boundary conditions.
+    intype = Iin.dtype
+    hcol = array([1.0, 4.0, 1.0], np.float32) / 6.0
+    if intype == np.complex128:
+        Iin = Iin.astype(np.complex64)
+
+    ck = cspline2d(Iin, lmbda)
+    out = sepfir2d(ck, hcol, hcol)
+    out = out.astype(intype)
+    return out
+
+
+_splinefunc_cache = {}
+
+
+def gauss_spline(x, n):
+    r"""Gaussian approximation to B-spline basis function of order n.
+
+    Parameters
+    ----------
+    x : array_like
+        a knot vector
+    n : int
+        The order of the spline. Must be non-negative, i.e., n >= 0
+
+    Returns
+    -------
+    res : ndarray
+        B-spline basis function values approximated by a zero-mean Gaussian
+        function.
+
+    Notes
+    -----
+    The B-spline basis function can be approximated well by a zero-mean
+    Gaussian function with standard-deviation equal to :math:`\sigma=(n+1)/12`
+    for large `n` :
+
+    .. math::  \frac{1}{\sqrt {2\pi\sigma^2}}exp(-\frac{x^2}{2\sigma})
+
+    References
+    ----------
+    .. [1] Bouma H., Vilanova A., Bescos J.O., ter Haar Romeny B.M., Gerritsen
+       F.A. (2007) Fast and Accurate Gaussian Derivatives Based on B-Splines. In:
+       Sgallari F., Murli A., Paragios N. (eds) Scale Space and Variational
+       Methods in Computer Vision. SSVM 2007. Lecture Notes in Computer
+       Science, vol 4485. Springer, Berlin, Heidelberg
+    .. [2] http://folk.uio.no/inf3330/scripting/doc/python/SciPy/tutorial/old/node24.html
+
+    Examples
+    --------
+    We can calculate B-Spline basis functions approximated by a gaussian
+    distribution:
+
+    >>> import numpy as np
+    >>> from scipy.signal import gauss_spline
+    >>> knots = np.array([-1.0, 0.0, -1.0])
+    >>> gauss_spline(knots, 3)
+    array([0.15418033, 0.6909883, 0.15418033])  # may vary
+
+    """
+    x = asarray(x)
+    signsq = (n + 1) / 12.0
+    return 1 / sqrt(2 * pi * signsq) * exp(-x ** 2 / 2 / signsq)
+
+
+def _cubic(x):
+    x = asarray(x, dtype=float)
+    b = BSpline.basis_element([-2, -1, 0, 1, 2], extrapolate=False)
+    out = b(x)
+    out[(x < -2) | (x > 2)] = 0
+    return out
+
+
+def _quadratic(x):
+    x = abs(asarray(x, dtype=float))
+    b = BSpline.basis_element([-1.5, -0.5, 0.5, 1.5], extrapolate=False)
+    out = b(x)
+    out[(x < -1.5) | (x > 1.5)] = 0
+    return out
+
+
+def _coeff_smooth(lam):
+    xi = 1 - 96 * lam + 24 * lam * sqrt(3 + 144 * lam)
+    omeg = arctan2(sqrt(144 * lam - 1), sqrt(xi))
+    rho = (24 * lam - 1 - sqrt(xi)) / (24 * lam)
+    rho = rho * sqrt((48 * lam + 24 * lam * sqrt(3 + 144 * lam)) / xi)
+    return rho, omeg
+
+
+def _hc(k, cs, rho, omega):
+    return (cs / sin(omega) * (rho ** k) * sin(omega * (k + 1)) *
+            greater(k, -1))
+
+
+def _hs(k, cs, rho, omega):
+    c0 = (cs * cs * (1 + rho * rho) / (1 - rho * rho) /
+          (1 - 2 * rho * rho * cos(2 * omega) + rho ** 4))
+    gamma = (1 - rho * rho) / (1 + rho * rho) / tan(omega)
+    ak = abs(k)
+    return c0 * rho ** ak * (cos(omega * ak) + gamma * sin(omega * ak))
+
+
+def _cubic_smooth_coeff(signal, lamb):
+    rho, omega = _coeff_smooth(lamb)
+    cs = 1 - 2 * rho * cos(omega) + rho * rho
+    K = len(signal)
+    k = arange(K)
+
+    zi_2 = (_hc(0, cs, rho, omega) * signal[0] +
+            add.reduce(_hc(k + 1, cs, rho, omega) * signal))
+    zi_1 = (_hc(0, cs, rho, omega) * signal[0] +
+            _hc(1, cs, rho, omega) * signal[1] +
+            add.reduce(_hc(k + 2, cs, rho, omega) * signal))
+
+    # Forward filter:
+    # for n in range(2, K):
+    #     yp[n] = (cs * signal[n] + 2 * rho * cos(omega) * yp[n - 1] -
+    #              rho * rho * yp[n - 2])
+    zi = lfiltic(cs, r_[1, -2 * rho * cos(omega), rho * rho], r_[zi_1, zi_2])
+    zi = zi.reshape(1, -1)
+
+    sos = r_[cs, 0, 0, 1, -2 * rho * cos(omega), rho * rho]
+    sos = sos.reshape(1, -1)
+
+    yp, _ = sosfilt(sos, signal[2:], zi=zi)
+    yp = r_[zi_2, zi_1, yp]
+
+    # Reverse filter:
+    # for n in range(K - 3, -1, -1):
+    #     y[n] = (cs * yp[n] + 2 * rho * cos(omega) * y[n + 1] -
+    #             rho * rho * y[n + 2])
+
+    zi_2 = add.reduce((_hs(k, cs, rho, omega) +
+                       _hs(k + 1, cs, rho, omega)) * signal[::-1])
+    zi_1 = add.reduce((_hs(k - 1, cs, rho, omega) +
+                       _hs(k + 2, cs, rho, omega)) * signal[::-1])
+
+    zi = lfiltic(cs, r_[1, -2 * rho * cos(omega), rho * rho], r_[zi_1, zi_2])
+    zi = zi.reshape(1, -1)
+    y, _ = sosfilt(sos, yp[-3::-1], zi=zi)
+    y = r_[y[::-1], zi_1, zi_2]
+    return y
+
+
+def _cubic_coeff(signal):
+    zi = -2 + sqrt(3)
+    K = len(signal)
+    powers = zi ** arange(K)
+
+    if K == 1:
+        yplus = signal[0] + zi * add.reduce(powers * signal)
+        output = zi / (zi - 1) * yplus
+        return atleast_1d(output)
+
+    # Forward filter:
+    # yplus[0] = signal[0] + zi * add.reduce(powers * signal)
+    # for k in range(1, K):
+    #     yplus[k] = signal[k] + zi * yplus[k - 1]
+
+    state = lfiltic(1, r_[1, -zi], atleast_1d(add.reduce(powers * signal)))
+
+    b = ones(1)
+    a = r_[1, -zi]
+    yplus, _ = lfilter(b, a, signal, zi=state)
+
+    # Reverse filter:
+    # output[K - 1] = zi / (zi - 1) * yplus[K - 1]
+    # for k in range(K - 2, -1, -1):
+    #     output[k] = zi * (output[k + 1] - yplus[k])
+    out_last = zi / (zi - 1) * yplus[K - 1]
+    state = lfiltic(-zi, r_[1, -zi], atleast_1d(out_last))
+
+    b = asarray([-zi])
+    output, _ = lfilter(b, a, yplus[-2::-1], zi=state)
+    output = r_[output[::-1], out_last]
+    return output * 6.0
+
+
+def _quadratic_coeff(signal):
+    zi = -3 + 2 * sqrt(2.0)
+    K = len(signal)
+    powers = zi ** arange(K)
+
+    if K == 1:
+        yplus = signal[0] + zi * add.reduce(powers * signal)
+        output = zi / (zi - 1) * yplus
+        return atleast_1d(output)
+
+    # Forward filter:
+    # yplus[0] = signal[0] + zi * add.reduce(powers * signal)
+    # for k in range(1, K):
+    #     yplus[k] = signal[k] + zi * yplus[k - 1]
+
+    state = lfiltic(1, r_[1, -zi], atleast_1d(add.reduce(powers * signal)))
+
+    b = ones(1)
+    a = r_[1, -zi]
+    yplus, _ = lfilter(b, a, signal, zi=state)
+
+    # Reverse filter:
+    # output[K - 1] = zi / (zi - 1) * yplus[K - 1]
+    # for k in range(K - 2, -1, -1):
+    #     output[k] = zi * (output[k + 1] - yplus[k])
+    out_last = zi / (zi - 1) * yplus[K - 1]
+    state = lfiltic(-zi, r_[1, -zi], atleast_1d(out_last))
+
+    b = asarray([-zi])
+    output, _ = lfilter(b, a, yplus[-2::-1], zi=state)
+    output = r_[output[::-1], out_last]
+    return output * 8.0
+
+
+def compute_root_from_lambda(lamb):
+    tmp = sqrt(3 + 144 * lamb)
+    xi = 1 - 96 * lamb + 24 * lamb * tmp
+    omega = arctan(sqrt((144 * lamb - 1.0) / xi))
+    tmp2 = sqrt(xi)
+    r = ((24 * lamb - 1 - tmp2) / (24 * lamb) *
+         sqrt(48*lamb + 24 * lamb * tmp) / tmp2)
+    return r, omega
+
+
+def cspline1d(signal, lamb=0.0):
+    """
+    Compute cubic spline coefficients for rank-1 array.
+
+    Find the cubic spline coefficients for a 1-D signal assuming
+    mirror-symmetric boundary conditions. To obtain the signal back from the
+    spline representation mirror-symmetric-convolve these coefficients with a
+    length 3 FIR window [1.0, 4.0, 1.0]/ 6.0 .
+
+    Parameters
+    ----------
+    signal : ndarray
+        A rank-1 array representing samples of a signal.
+    lamb : float, optional
+        Smoothing coefficient, default is 0.0.
+
+    Returns
+    -------
+    c : ndarray
+        Cubic spline coefficients.
+
+    See Also
+    --------
+    cspline1d_eval : Evaluate a cubic spline at the new set of points.
+
+    Examples
+    --------
+    We can filter a signal to reduce and smooth out high-frequency noise with
+    a cubic spline:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.signal import cspline1d, cspline1d_eval
+    >>> rng = np.random.default_rng()
+    >>> sig = np.repeat([0., 1., 0.], 100)
+    >>> sig += rng.standard_normal(len(sig))*0.05  # add noise
+    >>> time = np.linspace(0, len(sig))
+    >>> filtered = cspline1d_eval(cspline1d(sig), time)
+    >>> plt.plot(sig, label="signal")
+    >>> plt.plot(time, filtered, label="filtered")
+    >>> plt.legend()
+    >>> plt.show()
+
+    """
+    if lamb != 0.0:
+        return _cubic_smooth_coeff(signal, lamb)
+    else:
+        return _cubic_coeff(signal)
+
+
+def qspline1d(signal, lamb=0.0):
+    """Compute quadratic spline coefficients for rank-1 array.
+
+    Parameters
+    ----------
+    signal : ndarray
+        A rank-1 array representing samples of a signal.
+    lamb : float, optional
+        Smoothing coefficient (must be zero for now).
+
+    Returns
+    -------
+    c : ndarray
+        Quadratic spline coefficients.
+
+    See Also
+    --------
+    qspline1d_eval : Evaluate a quadratic spline at the new set of points.
+
+    Notes
+    -----
+    Find the quadratic spline coefficients for a 1-D signal assuming
+    mirror-symmetric boundary conditions. To obtain the signal back from the
+    spline representation mirror-symmetric-convolve these coefficients with a
+    length 3 FIR window [1.0, 6.0, 1.0]/ 8.0 .
+
+    Examples
+    --------
+    We can filter a signal to reduce and smooth out high-frequency noise with
+    a quadratic spline:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.signal import qspline1d, qspline1d_eval
+    >>> rng = np.random.default_rng()
+    >>> sig = np.repeat([0., 1., 0.], 100)
+    >>> sig += rng.standard_normal(len(sig))*0.05  # add noise
+    >>> time = np.linspace(0, len(sig))
+    >>> filtered = qspline1d_eval(qspline1d(sig), time)
+    >>> plt.plot(sig, label="signal")
+    >>> plt.plot(time, filtered, label="filtered")
+    >>> plt.legend()
+    >>> plt.show()
+
+    """
+    if lamb != 0.0:
+        raise ValueError("Smoothing quadratic splines not supported yet.")
+    else:
+        return _quadratic_coeff(signal)
+
+
+def collapse_2d(x, axis):
+    x = moveaxis(x, axis, -1)
+    x_shape = x.shape
+    x = x.reshape(-1, x.shape[-1])
+    if not x.flags.c_contiguous:
+        x = x.copy()
+    return x, x_shape
+
+
+def symiirorder_nd(func, input, *args, axis=-1, **kwargs):
+    axis = normalize_axis_index(axis, input.ndim)
+    input_shape = input.shape
+    input_ndim = input.ndim
+    if input.ndim > 1:
+        input, input_shape = collapse_2d(input, axis)
+
+    out = func(input, *args, **kwargs)
+
+    if input_ndim > 1:
+        out = out.reshape(input_shape)
+        out = moveaxis(out, -1, axis)
+        if not out.flags.c_contiguous:
+            out = out.copy()
+    return out
+
+
+def qspline2d(signal, lamb=0.0, precision=-1.0):
+    """
+    Coefficients for 2-D quadratic (2nd order) B-spline.
+
+    Return the second-order B-spline coefficients over a regularly spaced
+    input grid for the two-dimensional input image.
+
+    Parameters
+    ----------
+    input : ndarray
+        The input signal.
+    lamb : float
+        Specifies the amount of smoothing in the transfer function.
+    precision : float
+        Specifies the precision for computing the infinite sum needed to apply
+        mirror-symmetric boundary conditions.
+
+    Returns
+    -------
+    output : ndarray
+        The filtered signal.
+    """
+    if precision < 0.0 or precision >= 1.0:
+        if signal.dtype in [float32, complex64]:
+            precision = 1e-3
+        else:
+            precision = 1e-6
+
+    if lamb > 0:
+        raise ValueError('lambda must be negative or zero')
+
+    # normal quadratic spline
+    r = -3 + 2 * sqrt(2.0)
+    c0 = -r * 8.0
+    z1 = r
+
+    out = symiirorder_nd(symiirorder1, signal, c0, z1, precision, axis=-1)
+    out = symiirorder_nd(symiirorder1, out, c0, z1, precision, axis=0)
+    return out
+
+
+def cspline2d(signal, lamb=0.0, precision=-1.0):
+    """
+    Coefficients for 2-D cubic (3rd order) B-spline.
+
+    Return the third-order B-spline coefficients over a regularly spaced
+    input grid for the two-dimensional input image.
+
+    Parameters
+    ----------
+    input : ndarray
+        The input signal.
+    lamb : float
+        Specifies the amount of smoothing in the transfer function.
+    precision : float
+        Specifies the precision for computing the infinite sum needed to apply
+        mirror-symmetric boundary conditions.
+
+    Returns
+    -------
+    output : ndarray
+        The filtered signal.
+    """
+    if precision < 0.0 or precision >= 1.0:
+        if signal.dtype in [float32, complex64]:
+            precision = 1e-3
+        else:
+            precision = 1e-6
+
+    if lamb <= 1 / 144.0:
+        # Normal cubic spline
+        r = -2 + sqrt(3.0)
+        out = symiirorder_nd(
+            symiirorder1, signal, -r * 6.0, r, precision=precision, axis=-1)
+        out = symiirorder_nd(
+            symiirorder1, out, -r * 6.0, r, precision=precision, axis=0)
+        return out
+
+    r, omega = compute_root_from_lambda(lamb)
+    out = symiirorder_nd(symiirorder2, signal, r, omega,
+                         precision=precision, axis=-1)
+    out = symiirorder_nd(symiirorder2, out, r, omega,
+                         precision=precision, axis=0)
+    return out
+
+
+def cspline1d_eval(cj, newx, dx=1.0, x0=0):
+    """Evaluate a cubic spline at the new set of points.
+
+    `dx` is the old sample-spacing while `x0` was the old origin. In
+    other-words the old-sample points (knot-points) for which the `cj`
+    represent spline coefficients were at equally-spaced points of:
+
+      oldx = x0 + j*dx  j=0...N-1, with N=len(cj)
+
+    Edges are handled using mirror-symmetric boundary conditions.
+
+    Parameters
+    ----------
+    cj : ndarray
+        cublic spline coefficients
+    newx : ndarray
+        New set of points.
+    dx : float, optional
+        Old sample-spacing, the default value is 1.0.
+    x0 : int, optional
+        Old origin, the default value is 0.
+
+    Returns
+    -------
+    res : ndarray
+        Evaluated a cubic spline points.
+
+    See Also
+    --------
+    cspline1d : Compute cubic spline coefficients for rank-1 array.
+
+    Examples
+    --------
+    We can filter a signal to reduce and smooth out high-frequency noise with
+    a cubic spline:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.signal import cspline1d, cspline1d_eval
+    >>> rng = np.random.default_rng()
+    >>> sig = np.repeat([0., 1., 0.], 100)
+    >>> sig += rng.standard_normal(len(sig))*0.05  # add noise
+    >>> time = np.linspace(0, len(sig))
+    >>> filtered = cspline1d_eval(cspline1d(sig), time)
+    >>> plt.plot(sig, label="signal")
+    >>> plt.plot(time, filtered, label="filtered")
+    >>> plt.legend()
+    >>> plt.show()
+
+    """
+    newx = (asarray(newx) - x0) / float(dx)
+    res = zeros_like(newx, dtype=cj.dtype)
+    if res.size == 0:
+        return res
+    N = len(cj)
+    cond1 = newx < 0
+    cond2 = newx > (N - 1)
+    cond3 = ~(cond1 | cond2)
+    # handle general mirror-symmetry
+    res[cond1] = cspline1d_eval(cj, -newx[cond1])
+    res[cond2] = cspline1d_eval(cj, 2 * (N - 1) - newx[cond2])
+    newx = newx[cond3]
+    if newx.size == 0:
+        return res
+    result = zeros_like(newx, dtype=cj.dtype)
+    jlower = floor(newx - 2).astype(int) + 1
+    for i in range(4):
+        thisj = jlower + i
+        indj = thisj.clip(0, N - 1)  # handle edge cases
+        result += cj[indj] * _cubic(newx - thisj)
+    res[cond3] = result
+    return res
+
+
+def qspline1d_eval(cj, newx, dx=1.0, x0=0):
+    """Evaluate a quadratic spline at the new set of points.
+
+    Parameters
+    ----------
+    cj : ndarray
+        Quadratic spline coefficients
+    newx : ndarray
+        New set of points.
+    dx : float, optional
+        Old sample-spacing, the default value is 1.0.
+    x0 : int, optional
+        Old origin, the default value is 0.
+
+    Returns
+    -------
+    res : ndarray
+        Evaluated a quadratic spline points.
+
+    See Also
+    --------
+    qspline1d : Compute quadratic spline coefficients for rank-1 array.
+
+    Notes
+    -----
+    `dx` is the old sample-spacing while `x0` was the old origin. In
+    other-words the old-sample points (knot-points) for which the `cj`
+    represent spline coefficients were at equally-spaced points of::
+
+      oldx = x0 + j*dx  j=0...N-1, with N=len(cj)
+
+    Edges are handled using mirror-symmetric boundary conditions.
+
+    Examples
+    --------
+    We can filter a signal to reduce and smooth out high-frequency noise with
+    a quadratic spline:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.signal import qspline1d, qspline1d_eval
+    >>> rng = np.random.default_rng()
+    >>> sig = np.repeat([0., 1., 0.], 100)
+    >>> sig += rng.standard_normal(len(sig))*0.05  # add noise
+    >>> time = np.linspace(0, len(sig))
+    >>> filtered = qspline1d_eval(qspline1d(sig), time)
+    >>> plt.plot(sig, label="signal")
+    >>> plt.plot(time, filtered, label="filtered")
+    >>> plt.legend()
+    >>> plt.show()
+
+    """
+    newx = (asarray(newx) - x0) / dx
+    res = zeros_like(newx)
+    if res.size == 0:
+        return res
+    N = len(cj)
+    cond1 = newx < 0
+    cond2 = newx > (N - 1)
+    cond3 = ~(cond1 | cond2)
+    # handle general mirror-symmetry
+    res[cond1] = qspline1d_eval(cj, -newx[cond1])
+    res[cond2] = qspline1d_eval(cj, 2 * (N - 1) - newx[cond2])
+    newx = newx[cond3]
+    if newx.size == 0:
+        return res
+    result = zeros_like(newx)
+    jlower = floor(newx - 1.5).astype(int) + 1
+    for i in range(3):
+        thisj = jlower + i
+        indj = thisj.clip(0, N - 1)  # handle edge cases
+        result += cj[indj] * _quadratic(newx - thisj)
+    res[cond3] = result
+    return res
+
+
+def symiirorder1(signal, c0, z1, precision=-1.0):
+    """
+    Implement a smoothing IIR filter with mirror-symmetric boundary conditions
+    using a cascade of first-order sections.
+
+    The second section uses a reversed sequence.  This implements a system with
+    the following transfer function and mirror-symmetric boundary conditions::
+
+                           c0
+           H(z) = ---------------------
+                   (1-z1/z) (1 - z1 z)
+
+    The resulting signal will have mirror symmetric boundary conditions
+    as well.
+
+    Parameters
+    ----------
+    signal : ndarray
+        The input signal. If 2D, then the filter will be applied in a batched
+        fashion across the last axis.
+    c0, z1 : scalar
+        Parameters in the transfer function.
+    precision :
+        Specifies the precision for calculating initial conditions
+        of the recursive filter based on mirror-symmetric input.
+
+    Returns
+    -------
+    output : ndarray
+        The filtered signal.
+    """
+    if np.abs(z1) >= 1:
+        raise ValueError('|z1| must be less than 1.0')
+
+    if signal.ndim > 2:
+        raise ValueError('Input must be 1D or 2D')
+
+    squeeze_dim = False
+    if signal.ndim == 1:
+        signal = signal[None, :]
+        squeeze_dim = True
+
+    if np.issubdtype(signal.dtype, np.integer):
+        signal = signal.astype(np.promote_types(signal.dtype, np.float32))
+
+    y0 = symiirorder1_ic(signal, z1, precision)
+
+    # Apply first the system 1 / (1 - z1 * z^-1)
+    b = np.ones(1, dtype=signal.dtype)
+    a = np.r_[1, -z1]
+    a = a.astype(signal.dtype)
+
+    # Compute the initial state for lfilter.
+    zii = y0 * z1
+
+    y1, _ = lfilter(b, a, axis_slice(signal, 1), zi=zii)
+    y1 = np.c_[y0, y1]
+
+    # Compute backward symmetric condition and apply the system
+    # c0 / (1 - z1 * z)
+    b = np.asarray([c0], dtype=signal.dtype)
+    out_last = -c0 / (z1 - 1.0) * axis_slice(y1, -1)
+
+    # Compute the initial state for lfilter.
+    zii = out_last * z1
+
+    # Apply the system c0 / (1 - z1 * z) by reversing the output of the previous stage
+    out, _ = lfilter(b, a, axis_slice(y1, -2, step=-1), zi=zii)
+    out = np.c_[axis_reverse(out), out_last]
+
+    if squeeze_dim:
+        out = out[0]
+
+    return out
+
+
+def symiirorder2(input, r, omega, precision=-1.0):
+    """
+    Implement a smoothing IIR filter with mirror-symmetric boundary conditions
+    using a cascade of second-order sections.
+
+    The second section uses a reversed sequence.  This implements the following
+    transfer function::
+
+                                  cs^2
+         H(z) = ---------------------------------------
+                (1 - a2/z - a3/z^2) (1 - a2 z - a3 z^2 )
+
+    where::
+
+          a2 = 2 * r * cos(omega)
+          a3 = - r ** 2
+          cs = 1 - 2 * r * cos(omega) + r ** 2
+
+    Parameters
+    ----------
+    input : ndarray
+        The input signal.
+    r, omega : float
+        Parameters in the transfer function.
+    precision : float
+        Specifies the precision for calculating initial conditions
+        of the recursive filter based on mirror-symmetric input.
+
+    Returns
+    -------
+    output : ndarray
+        The filtered signal.
+    """
+    if r >= 1.0:
+        raise ValueError('r must be less than 1.0')
+
+    if input.ndim > 2:
+        raise ValueError('Input must be 1D or 2D')
+
+    if not input.flags.c_contiguous:
+        input = input.copy()
+
+    squeeze_dim = False
+    if input.ndim == 1:
+        input = input[None, :]
+        squeeze_dim = True
+
+    if np.issubdtype(input.dtype, np.integer):
+        input = input.astype(np.promote_types(input.dtype, np.float32))
+
+    rsq = r * r
+    a2 = 2 * r * np.cos(omega)
+    a3 = -rsq
+    cs = np.atleast_1d(1 - 2 * r * np.cos(omega) + rsq)
+    sos = np.atleast_2d(np.r_[cs, 0, 0, 1, -a2, -a3]).astype(input.dtype)
+
+    # Find the starting (forward) conditions.
+    ic_fwd = symiirorder2_ic_fwd(input, r, omega, precision)
+
+    # Apply first the system cs / (1 - a2 * z^-1 - a3 * z^-2)
+    # Compute the initial conditions in the form expected by sosfilt
+    # coef = np.asarray([[a3, a2], [0, a3]], dtype=input.dtype)
+    coef = np.r_[a3, a2, 0, a3].reshape(2, 2).astype(input.dtype)
+    zi = np.matmul(coef, ic_fwd[:, :, None])[:, :, 0]
+
+    y_fwd, _ = sosfilt(sos, axis_slice(input, 2), zi=zi[None])
+    y_fwd = np.c_[ic_fwd, y_fwd]
+
+    # Then compute the symmetric backward starting conditions
+    ic_bwd = symiirorder2_ic_bwd(input, r, omega, precision)
+
+    # Apply the system cs / (1 - a2 * z^1 - a3 * z^2)
+    # Compute the initial conditions in the form expected by sosfilt
+    zi = np.matmul(coef, ic_bwd[:, :, None])[:, :, 0]
+    y, _ = sosfilt(sos, axis_slice(y_fwd, -3, step=-1), zi=zi[None])
+    out = np.c_[axis_reverse(y), axis_reverse(ic_bwd)]
+
+    if squeeze_dim:
+        out = out[0]
+
+    return out

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_upfirdn.py

@@ -0,0 +1,216 @@
+# Code adapted from "upfirdn" python library with permission:
+#
+# Copyright (c) 2009, Motorola, Inc
+#
+# All Rights Reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+# * Redistributions of source code must retain the above copyright notice,
+# this list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# * Neither the name of Motorola nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+# IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+import numpy as np
+
+from ._upfirdn_apply import _output_len, _apply, mode_enum
+
+__all__ = ['upfirdn', '_output_len']
+
+_upfirdn_modes = [
+    'constant', 'wrap', 'edge', 'smooth', 'symmetric', 'reflect',
+    'antisymmetric', 'antireflect', 'line',
+]
+
+
+def _pad_h(h, up):
+    """Store coefficients in a transposed, flipped arrangement.
+
+    For example, suppose upRate is 3, and the
+    input number of coefficients is 10, represented as h[0], ..., h[9].
+
+    Then the internal buffer will look like this::
+
+       h[9], h[6], h[3], h[0],   // flipped phase 0 coefs
+       0,    h[7], h[4], h[1],   // flipped phase 1 coefs (zero-padded)
+       0,    h[8], h[5], h[2],   // flipped phase 2 coefs (zero-padded)
+
+    """
+    h_padlen = len(h) + (-len(h) % up)
+    h_full = np.zeros(h_padlen, h.dtype)
+    h_full[:len(h)] = h
+    h_full = h_full.reshape(-1, up).T[:, ::-1].ravel()
+    return h_full
+
+
+def _check_mode(mode):
+    mode = mode.lower()
+    enum = mode_enum(mode)
+    return enum
+
+
+class _UpFIRDn:
+    """Helper for resampling."""
+
+    def __init__(self, h, x_dtype, up, down):
+        h = np.asarray(h)
+        if h.ndim != 1 or h.size == 0:
+            raise ValueError('h must be 1-D with non-zero length')
+        self._output_type = np.result_type(h.dtype, x_dtype, np.float32)
+        h = np.asarray(h, self._output_type)
+        self._up = int(up)
+        self._down = int(down)
+        if self._up < 1 or self._down < 1:
+            raise ValueError('Both up and down must be >= 1')
+        # This both transposes, and "flips" each phase for filtering
+        self._h_trans_flip = _pad_h(h, self._up)
+        self._h_trans_flip = np.ascontiguousarray(self._h_trans_flip)
+        self._h_len_orig = len(h)
+
+    def apply_filter(self, x, axis=-1, mode='constant', cval=0):
+        """Apply the prepared filter to the specified axis of N-D signal x."""
+        output_len = _output_len(self._h_len_orig, x.shape[axis],
+                                 self._up, self._down)
+        # Explicit use of np.int64 for output_shape dtype avoids OverflowError
+        # when allocating large array on platforms where intp is 32 bits.
+        output_shape = np.asarray(x.shape, dtype=np.int64)
+        output_shape[axis] = output_len
+        out = np.zeros(output_shape, dtype=self._output_type, order='C')
+        axis = axis % x.ndim
+        mode = _check_mode(mode)
+        _apply(np.asarray(x, self._output_type),
+               self._h_trans_flip, out,
+               self._up, self._down, axis, mode, cval)
+        return out
+
+
+def upfirdn(h, x, up=1, down=1, axis=-1, mode='constant', cval=0):
+    """Upsample, FIR filter, and downsample.
+
+    Parameters
+    ----------
+    h : array_like
+        1-D FIR (finite-impulse response) filter coefficients.
+    x : array_like
+        Input signal array.
+    up : int, optional
+        Upsampling rate. Default is 1.
+    down : int, optional
+        Downsampling rate. Default is 1.
+    axis : int, optional
+        The axis of the input data array along which to apply the
+        linear filter. The filter is applied to each subarray along
+        this axis. Default is -1.
+    mode : str, optional
+        The signal extension mode to use. The set
+        ``{"constant", "symmetric", "reflect", "edge", "wrap"}`` correspond to
+        modes provided by `numpy.pad`. ``"smooth"`` implements a smooth
+        extension by extending based on the slope of the last 2 points at each
+        end of the array. ``"antireflect"`` and ``"antisymmetric"`` are
+        anti-symmetric versions of ``"reflect"`` and ``"symmetric"``. The mode
+        `"line"` extends the signal based on a linear trend defined by the
+        first and last points along the ``axis``.
+
+        .. versionadded:: 1.4.0
+    cval : float, optional
+        The constant value to use when ``mode == "constant"``.
+
+        .. versionadded:: 1.4.0
+
+    Returns
+    -------
+    y : ndarray
+        The output signal array. Dimensions will be the same as `x` except
+        for along `axis`, which will change size according to the `h`,
+        `up`,  and `down` parameters.
+
+    Notes
+    -----
+    The algorithm is an implementation of the block diagram shown on page 129
+    of the Vaidyanathan text [1]_ (Figure 4.3-8d).
+
+    The direct approach of upsampling by factor of P with zero insertion,
+    FIR filtering of length ``N``, and downsampling by factor of Q is
+    O(N*Q) per output sample. The polyphase implementation used here is
+    O(N/P).
+
+    .. versionadded:: 0.18
+
+    References
+    ----------
+    .. [1] P. P. Vaidyanathan, Multirate Systems and Filter Banks,
+           Prentice Hall, 1993.
+
+    Examples
+    --------
+    Simple operations:
+
+    >>> import numpy as np
+    >>> from scipy.signal import upfirdn
+    >>> upfirdn([1, 1, 1], [1, 1, 1])   # FIR filter
+    array([ 1.,  2.,  3.,  2.,  1.])
+    >>> upfirdn([1], [1, 2, 3], 3)  # upsampling with zeros insertion
+    array([ 1.,  0.,  0.,  2.,  0.,  0.,  3.])
+    >>> upfirdn([1, 1, 1], [1, 2, 3], 3)  # upsampling with sample-and-hold
+    array([ 1.,  1.,  1.,  2.,  2.,  2.,  3.,  3.,  3.])
+    >>> upfirdn([.5, 1, .5], [1, 1, 1], 2)  # linear interpolation
+    array([ 0.5,  1. ,  1. ,  1. ,  1. ,  1. ,  0.5])
+    >>> upfirdn([1], np.arange(10), 1, 3)  # decimation by 3
+    array([ 0.,  3.,  6.,  9.])
+    >>> upfirdn([.5, 1, .5], np.arange(10), 2, 3)  # linear interp, rate 2/3
+    array([ 0. ,  1. ,  2.5,  4. ,  5.5,  7. ,  8.5])
+
+    Apply a single filter to multiple signals:
+
+    >>> x = np.reshape(np.arange(8), (4, 2))
+    >>> x
+    array([[0, 1],
+           [2, 3],
+           [4, 5],
+           [6, 7]])
+
+    Apply along the last dimension of ``x``:
+
+    >>> h = [1, 1]
+    >>> upfirdn(h, x, 2)
+    array([[ 0.,  0.,  1.,  1.],
+           [ 2.,  2.,  3.,  3.],
+           [ 4.,  4.,  5.,  5.],
+           [ 6.,  6.,  7.,  7.]])
+
+    Apply along the 0th dimension of ``x``:
+
+    >>> upfirdn(h, x, 2, axis=0)
+    array([[ 0.,  1.],
+           [ 0.,  1.],
+           [ 2.,  3.],
+           [ 2.,  3.],
+           [ 4.,  5.],
+           [ 4.,  5.],
+           [ 6.,  7.],
+           [ 6.,  7.]])
+    """
+    x = np.asarray(x)
+    ufd = _UpFIRDn(h, x.dtype, up, down)
+    # This is equivalent to (but faster than) using np.apply_along_axis
+    return ufd.apply_filter(x, axis, mode, cval)

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_waveforms.py

@@ -0,0 +1,696 @@
+# Author: Travis Oliphant
+# 2003
+#
+# Feb. 2010: Updated by Warren Weckesser:
+#   Rewrote much of chirp()
+#   Added sweep_poly()
+import numpy as np
+from numpy import asarray, zeros, place, nan, mod, pi, extract, log, sqrt, \
+    exp, cos, sin, polyval, polyint
+
+
+__all__ = ['sawtooth', 'square', 'gausspulse', 'chirp', 'sweep_poly',
+           'unit_impulse']
+
+
+def sawtooth(t, width=1):
+    """
+    Return a periodic sawtooth or triangle waveform.
+
+    The sawtooth waveform has a period ``2*pi``, rises from -1 to 1 on the
+    interval 0 to ``width*2*pi``, then drops from 1 to -1 on the interval
+    ``width*2*pi`` to ``2*pi``. `width` must be in the interval [0, 1].
+
+    Note that this is not band-limited.  It produces an infinite number
+    of harmonics, which are aliased back and forth across the frequency
+    spectrum.
+
+    Parameters
+    ----------
+    t : array_like
+        Time.
+    width : array_like, optional
+        Width of the rising ramp as a proportion of the total cycle.
+        Default is 1, producing a rising ramp, while 0 produces a falling
+        ramp.  `width` = 0.5 produces a triangle wave.
+        If an array, causes wave shape to change over time, and must be the
+        same length as t.
+
+    Returns
+    -------
+    y : ndarray
+        Output array containing the sawtooth waveform.
+
+    Examples
+    --------
+    A 5 Hz waveform sampled at 500 Hz for 1 second:
+
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> import matplotlib.pyplot as plt
+    >>> t = np.linspace(0, 1, 500)
+    >>> plt.plot(t, signal.sawtooth(2 * np.pi * 5 * t))
+
+    """
+    t, w = asarray(t), asarray(width)
+    w = asarray(w + (t - t))
+    t = asarray(t + (w - w))
+    if t.dtype.char in ['fFdD']:
+        ytype = t.dtype.char
+    else:
+        ytype = 'd'
+    y = zeros(t.shape, ytype)
+
+    # width must be between 0 and 1 inclusive
+    mask1 = (w > 1) | (w < 0)
+    place(y, mask1, nan)
+
+    # take t modulo 2*pi
+    tmod = mod(t, 2 * pi)
+
+    # on the interval 0 to width*2*pi function is
+    #  tmod / (pi*w) - 1
+    mask2 = (1 - mask1) & (tmod < w * 2 * pi)
+    tsub = extract(mask2, tmod)
+    wsub = extract(mask2, w)
+    place(y, mask2, tsub / (pi * wsub) - 1)
+
+    # on the interval width*2*pi to 2*pi function is
+    #  (pi*(w+1)-tmod) / (pi*(1-w))
+
+    mask3 = (1 - mask1) & (1 - mask2)
+    tsub = extract(mask3, tmod)
+    wsub = extract(mask3, w)
+    place(y, mask3, (pi * (wsub + 1) - tsub) / (pi * (1 - wsub)))
+    return y
+
+
+def square(t, duty=0.5):
+    """
+    Return a periodic square-wave waveform.
+
+    The square wave has a period ``2*pi``, has value +1 from 0 to
+    ``2*pi*duty`` and -1 from ``2*pi*duty`` to ``2*pi``. `duty` must be in
+    the interval [0,1].
+
+    Note that this is not band-limited.  It produces an infinite number
+    of harmonics, which are aliased back and forth across the frequency
+    spectrum.
+
+    Parameters
+    ----------
+    t : array_like
+        The input time array.
+    duty : array_like, optional
+        Duty cycle.  Default is 0.5 (50% duty cycle).
+        If an array, causes wave shape to change over time, and must be the
+        same length as t.
+
+    Returns
+    -------
+    y : ndarray
+        Output array containing the square waveform.
+
+    Examples
+    --------
+    A 5 Hz waveform sampled at 500 Hz for 1 second:
+
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> import matplotlib.pyplot as plt
+    >>> t = np.linspace(0, 1, 500, endpoint=False)
+    >>> plt.plot(t, signal.square(2 * np.pi * 5 * t))
+    >>> plt.ylim(-2, 2)
+
+    A pulse-width modulated sine wave:
+
+    >>> plt.figure()
+    >>> sig = np.sin(2 * np.pi * t)
+    >>> pwm = signal.square(2 * np.pi * 30 * t, duty=(sig + 1)/2)
+    >>> plt.subplot(2, 1, 1)
+    >>> plt.plot(t, sig)
+    >>> plt.subplot(2, 1, 2)
+    >>> plt.plot(t, pwm)
+    >>> plt.ylim(-1.5, 1.5)
+
+    """
+    t, w = asarray(t), asarray(duty)
+    w = asarray(w + (t - t))
+    t = asarray(t + (w - w))
+    if t.dtype.char in ['fFdD']:
+        ytype = t.dtype.char
+    else:
+        ytype = 'd'
+
+    y = zeros(t.shape, ytype)
+
+    # width must be between 0 and 1 inclusive
+    mask1 = (w > 1) | (w < 0)
+    place(y, mask1, nan)
+
+    # on the interval 0 to duty*2*pi function is 1
+    tmod = mod(t, 2 * pi)
+    mask2 = (1 - mask1) & (tmod < w * 2 * pi)
+    place(y, mask2, 1)
+
+    # on the interval duty*2*pi to 2*pi function is
+    #  (pi*(w+1)-tmod) / (pi*(1-w))
+    mask3 = (1 - mask1) & (1 - mask2)
+    place(y, mask3, -1)
+    return y
+
+
+def gausspulse(t, fc=1000, bw=0.5, bwr=-6, tpr=-60, retquad=False,
+               retenv=False):
+    """
+    Return a Gaussian modulated sinusoid:
+
+        ``exp(-a t^2) exp(1j*2*pi*fc*t).``
+
+    If `retquad` is True, then return the real and imaginary parts
+    (in-phase and quadrature).
+    If `retenv` is True, then return the envelope (unmodulated signal).
+    Otherwise, return the real part of the modulated sinusoid.
+
+    Parameters
+    ----------
+    t : ndarray or the string 'cutoff'
+        Input array.
+    fc : float, optional
+        Center frequency (e.g. Hz).  Default is 1000.
+    bw : float, optional
+        Fractional bandwidth in frequency domain of pulse (e.g. Hz).
+        Default is 0.5.
+    bwr : float, optional
+        Reference level at which fractional bandwidth is calculated (dB).
+        Default is -6.
+    tpr : float, optional
+        If `t` is 'cutoff', then the function returns the cutoff
+        time for when the pulse amplitude falls below `tpr` (in dB).
+        Default is -60.
+    retquad : bool, optional
+        If True, return the quadrature (imaginary) as well as the real part
+        of the signal.  Default is False.
+    retenv : bool, optional
+        If True, return the envelope of the signal.  Default is False.
+
+    Returns
+    -------
+    yI : ndarray
+        Real part of signal.  Always returned.
+    yQ : ndarray
+        Imaginary part of signal.  Only returned if `retquad` is True.
+    yenv : ndarray
+        Envelope of signal.  Only returned if `retenv` is True.
+
+    Examples
+    --------
+    Plot real component, imaginary component, and envelope for a 5 Hz pulse,
+    sampled at 100 Hz for 2 seconds:
+
+    >>> import numpy as np
+    >>> from scipy import signal
+    >>> import matplotlib.pyplot as plt
+    >>> t = np.linspace(-1, 1, 2 * 100, endpoint=False)
+    >>> i, q, e = signal.gausspulse(t, fc=5, retquad=True, retenv=True)
+    >>> plt.plot(t, i, t, q, t, e, '--')
+
+    """
+    if fc < 0:
+        raise ValueError(f"Center frequency (fc={fc:.2f}) must be >=0.")
+    if bw <= 0:
+        raise ValueError(f"Fractional bandwidth (bw={bw:.2f}) must be > 0.")
+    if bwr >= 0:
+        raise ValueError(f"Reference level for bandwidth (bwr={bwr:.2f}) "
+                         "must be < 0 dB")
+
+    # exp(-a t^2) <->  sqrt(pi/a) exp(-pi^2/a * f^2)  = g(f)
+
+    ref = pow(10.0, bwr / 20.0)
+    # fdel = fc*bw/2:  g(fdel) = ref --- solve this for a
+    #
+    # pi^2/a * fc^2 * bw^2 /4=-log(ref)
+    a = -(pi * fc * bw) ** 2 / (4.0 * log(ref))
+
+    if isinstance(t, str):
+        if t == 'cutoff':  # compute cut_off point
+            #  Solve exp(-a tc**2) = tref  for tc
+            #   tc = sqrt(-log(tref) / a) where tref = 10^(tpr/20)
+            if tpr >= 0:
+                raise ValueError("Reference level for time cutoff must "
+                                 "be < 0 dB")
+            tref = pow(10.0, tpr / 20.0)
+            return sqrt(-log(tref) / a)
+        else:
+            raise ValueError("If `t` is a string, it must be 'cutoff'")
+
+    yenv = exp(-a * t * t)
+    yI = yenv * cos(2 * pi * fc * t)
+    yQ = yenv * sin(2 * pi * fc * t)
+    if not retquad and not retenv:
+        return yI
+    if not retquad and retenv:
+        return yI, yenv
+    if retquad and not retenv:
+        return yI, yQ
+    if retquad and retenv:
+        return yI, yQ, yenv
+
+
+def chirp(t, f0, t1, f1, method='linear', phi=0, vertex_zero=True, *,
+          complex=False):
+    r"""Frequency-swept cosine generator.
+
+    In the following, 'Hz' should be interpreted as 'cycles per unit';
+    there is no requirement here that the unit is one second.  The
+    important distinction is that the units of rotation are cycles, not
+    radians. Likewise, `t` could be a measurement of space instead of time.
+
+    Parameters
+    ----------
+    t : array_like
+        Times at which to evaluate the waveform.
+    f0 : float
+        Frequency (e.g. Hz) at time t=0.
+    t1 : float
+        Time at which `f1` is specified.
+    f1 : float
+        Frequency (e.g. Hz) of the waveform at time `t1`.
+    method : {'linear', 'quadratic', 'logarithmic', 'hyperbolic'}, optional
+        Kind of frequency sweep.  If not given, `linear` is assumed.  See
+        Notes below for more details.
+    phi : float, optional
+        Phase offset, in degrees. Default is 0.
+    vertex_zero : bool, optional
+        This parameter is only used when `method` is 'quadratic'.
+        It determines whether the vertex of the parabola that is the graph
+        of the frequency is at t=0 or t=t1.
+    complex : bool, optional
+        This parameter creates a complex-valued analytic signal instead of a
+        real-valued signal. It allows the use of complex baseband (in communications
+        domain). Default is False.
+
+        .. versionadded:: 1.15.0
+
+    Returns
+    -------
+    y : ndarray
+        A numpy array containing the signal evaluated at `t` with the requested
+        time-varying frequency.  More precisely, the function returns
+        ``exp(1j*phase + 1j*(pi/180)*phi) if complex else cos(phase + (pi/180)*phi)``
+        where `phase` is the integral (from 0 to `t`) of ``2*pi*f(t)``.
+        The instantaneous frequency ``f(t)`` is defined below.
+
+    See Also
+    --------
+    sweep_poly
+
+    Notes
+    -----
+    There are four possible options for the parameter `method`, which have a (long)
+    standard form and some allowed abbreviations. The formulas for the instantaneous
+    frequency :math:`f(t)` of the generated signal are as follows:
+
+    1. Parameter `method` in ``('linear', 'lin', 'li')``:
+
+       .. math::
+           f(t) = f_0 + \beta\, t           \quad\text{with}\quad
+           \beta = \frac{f_1 - f_0}{t_1}
+
+       Frequency :math:`f(t)` varies linearly over time with a constant rate
+       :math:`\beta`.
+
+    2. Parameter `method` in ``('quadratic', 'quad', 'q')``:
+
+       .. math::
+            f(t) =
+            \begin{cases}
+              f_0 + \beta\, t^2          & \text{if vertex_zero is True,}\\
+              f_1 + \beta\, (t_1 - t)^2  & \text{otherwise,}
+            \end{cases}
+            \quad\text{with}\quad
+            \beta = \frac{f_1 - f_0}{t_1^2}
+
+       The graph of the frequency f(t) is a parabola through :math:`(0, f_0)` and
+       :math:`(t_1, f_1)`.  By default, the vertex of the parabola is at
+       :math:`(0, f_0)`. If `vertex_zero` is ``False``, then the vertex is at
+       :math:`(t_1, f_1)`.
+       To use a more general quadratic function, or an arbitrary
+       polynomial, use the function `scipy.signal.sweep_poly`.
+
+    3. Parameter `method` in ``('logarithmic', 'log', 'lo')``:
+
+       .. math::
+            f(t) = f_0  \left(\frac{f_1}{f_0}\right)^{t/t_1}
+
+       :math:`f_0` and :math:`f_1` must be nonzero and have the same sign.
+       This signal is also known as a geometric or exponential chirp.
+
+    4. Parameter `method` in ``('hyperbolic', 'hyp')``:
+
+       .. math::
+              f(t) = \frac{\alpha}{\beta\, t + \gamma} \quad\text{with}\quad
+              \alpha = f_0 f_1 t_1, \ \beta = f_0 - f_1, \ \gamma = f_1 t_1
+
+       :math:`f_0` and :math:`f_1` must be nonzero.
+
+
+    Examples
+    --------
+    For the first example, a linear chirp ranging from 6 Hz to 1 Hz over 10 seconds is
+    plotted:
+
+    >>> import numpy as np
+    >>> from matplotlib.pyplot import tight_layout
+    >>> from scipy.signal import chirp, square, ShortTimeFFT
+    >>> from scipy.signal.windows import gaussian
+    >>> import matplotlib.pyplot as plt
+    ...
+    >>> N, T = 1000, 0.01  # number of samples and sampling interval for 10 s signal
+    >>> t = np.arange(N) * T  # timestamps
+    ...
+    >>> x_lin = chirp(t, f0=6, f1=1, t1=10, method='linear')
+    ...
+    >>> fg0, ax0 = plt.subplots()
+    >>> ax0.set_title(r"Linear Chirp from $f(0)=6\,$Hz to $f(10)=1\,$Hz")
+    >>> ax0.set(xlabel="Time $t$ in Seconds", ylabel=r"Amplitude $x_\text{lin}(t)$")
+    >>> ax0.plot(t, x_lin)
+    >>> plt.show()
+
+    The following four plots each show the short-time Fourier transform of a chirp
+    ranging from 45 Hz to 5 Hz with different values for the parameter `method`
+    (and `vertex_zero`):
+
+    >>> x_qu0 = chirp(t, f0=45, f1=5, t1=N*T, method='quadratic', vertex_zero=True)
+    >>> x_qu1 = chirp(t, f0=45, f1=5, t1=N*T, method='quadratic', vertex_zero=False)
+    >>> x_log = chirp(t, f0=45, f1=5, t1=N*T, method='logarithmic')
+    >>> x_hyp = chirp(t, f0=45, f1=5, t1=N*T, method='hyperbolic')
+    ...
+    >>> win = gaussian(50, std=12, sym=True)
+    >>> SFT = ShortTimeFFT(win, hop=2, fs=1/T, mfft=800, scale_to='magnitude')
+    >>> ts = ("'quadratic', vertex_zero=True", "'quadratic', vertex_zero=False",
+    ...       "'logarithmic'", "'hyperbolic'")
+    >>> fg1, ax1s = plt.subplots(2, 2, sharex='all', sharey='all',
+    ...                          figsize=(6, 5),  layout="constrained")
+    >>> for x_, ax_, t_ in zip([x_qu0, x_qu1, x_log, x_hyp], ax1s.ravel(), ts):
+    ...     aSx = abs(SFT.stft(x_))
+    ...     im_ = ax_.imshow(aSx, origin='lower', aspect='auto', extent=SFT.extent(N),
+    ...                      cmap='plasma')
+    ...     ax_.set_title(t_)
+    ...     if t_ == "'hyperbolic'":
+    ...         fg1.colorbar(im_, ax=ax1s, label='Magnitude $|S_z(t,f)|$')
+    >>> _ = fg1.supxlabel("Time $t$ in Seconds")  # `_ =` is needed to pass doctests
+    >>> _ = fg1.supylabel("Frequency $f$ in Hertz")
+    >>> plt.show()
+
+    Finally, the short-time Fourier transform of a complex-valued linear chirp
+    ranging from -30 Hz to 30 Hz is depicted:
+
+    >>> z_lin = chirp(t, f0=-30, f1=30, t1=N*T, method="linear", complex=True)
+    >>> SFT.fft_mode = 'centered'  # needed to work with complex signals
+    >>> aSz = abs(SFT.stft(z_lin))
+    ...
+    >>> fg2, ax2 = plt.subplots()
+    >>> ax2.set_title(r"Linear Chirp from $-30\,$Hz to $30\,$Hz")
+    >>> ax2.set(xlabel="Time $t$ in Seconds", ylabel="Frequency $f$ in Hertz")
+    >>> im2 = ax2.imshow(aSz, origin='lower', aspect='auto',
+    ...                  extent=SFT.extent(N), cmap='viridis')
+    >>> fg2.colorbar(im2, label='Magnitude $|S_z(t,f)|$')
+    >>> plt.show()
+
+    Note that using negative frequencies makes only sense with complex-valued signals.
+    Furthermore, the magnitude of the complex exponential function is one whereas the
+    magnitude of the real-valued cosine function is only 1/2.
+    """
+    # 'phase' is computed in _chirp_phase, to make testing easier.
+    phase = _chirp_phase(t, f0, t1, f1, method, vertex_zero) + np.deg2rad(phi)
+    return np.exp(1j*phase) if complex else np.cos(phase)
+
+
+def _chirp_phase(t, f0, t1, f1, method='linear', vertex_zero=True):
+    """
+    Calculate the phase used by `chirp` to generate its output.
+
+    See `chirp` for a description of the arguments.
+
+    """
+    t = asarray(t)
+    f0 = float(f0)
+    t1 = float(t1)
+    f1 = float(f1)
+    if method in ['linear', 'lin', 'li']:
+        beta = (f1 - f0) / t1
+        phase = 2 * pi * (f0 * t + 0.5 * beta * t * t)
+
+    elif method in ['quadratic', 'quad', 'q']:
+        beta = (f1 - f0) / (t1 ** 2)
+        if vertex_zero:
+            phase = 2 * pi * (f0 * t + beta * t ** 3 / 3)
+        else:
+            phase = 2 * pi * (f1 * t + beta * ((t1 - t) ** 3 - t1 ** 3) / 3)
+
+    elif method in ['logarithmic', 'log', 'lo']:
+        if f0 * f1 <= 0.0:
+            raise ValueError("For a logarithmic chirp, f0 and f1 must be "
+                             "nonzero and have the same sign.")
+        if f0 == f1:
+            phase = 2 * pi * f0 * t
+        else:
+            beta = t1 / log(f1 / f0)
+            phase = 2 * pi * beta * f0 * (pow(f1 / f0, t / t1) - 1.0)
+
+    elif method in ['hyperbolic', 'hyp']:
+        if f0 == 0 or f1 == 0:
+            raise ValueError("For a hyperbolic chirp, f0 and f1 must be "
+                             "nonzero.")
+        if f0 == f1:
+            # Degenerate case: constant frequency.
+            phase = 2 * pi * f0 * t
+        else:
+            # Singular point: the instantaneous frequency blows up
+            # when t == sing.
+            sing = -f1 * t1 / (f0 - f1)
+            phase = 2 * pi * (-sing * f0) * log(np.abs(1 - t/sing))
+
+    else:
+        raise ValueError("method must be 'linear', 'quadratic', 'logarithmic', "
+                         f"or 'hyperbolic', but a value of {method!r} was given.")
+
+    return phase
+
+
+def sweep_poly(t, poly, phi=0):
+    """
+    Frequency-swept cosine generator, with a time-dependent frequency.
+
+    This function generates a sinusoidal function whose instantaneous
+    frequency varies with time.  The frequency at time `t` is given by
+    the polynomial `poly`.
+
+    Parameters
+    ----------
+    t : ndarray
+        Times at which to evaluate the waveform.
+    poly : 1-D array_like or instance of numpy.poly1d
+        The desired frequency expressed as a polynomial.  If `poly` is
+        a list or ndarray of length n, then the elements of `poly` are
+        the coefficients of the polynomial, and the instantaneous
+        frequency is
+
+          ``f(t) = poly[0]*t**(n-1) + poly[1]*t**(n-2) + ... + poly[n-1]``
+
+        If `poly` is an instance of numpy.poly1d, then the
+        instantaneous frequency is
+
+          ``f(t) = poly(t)``
+
+    phi : float, optional
+        Phase offset, in degrees, Default: 0.
+
+    Returns
+    -------
+    sweep_poly : ndarray
+        A numpy array containing the signal evaluated at `t` with the
+        requested time-varying frequency.  More precisely, the function
+        returns ``cos(phase + (pi/180)*phi)``, where `phase` is the integral
+        (from 0 to t) of ``2 * pi * f(t)``; ``f(t)`` is defined above.
+
+    See Also
+    --------
+    chirp
+
+    Notes
+    -----
+    .. versionadded:: 0.8.0
+
+    If `poly` is a list or ndarray of length `n`, then the elements of
+    `poly` are the coefficients of the polynomial, and the instantaneous
+    frequency is:
+
+        ``f(t) = poly[0]*t**(n-1) + poly[1]*t**(n-2) + ... + poly[n-1]``
+
+    If `poly` is an instance of `numpy.poly1d`, then the instantaneous
+    frequency is:
+
+          ``f(t) = poly(t)``
+
+    Finally, the output `s` is:
+
+        ``cos(phase + (pi/180)*phi)``
+
+    where `phase` is the integral from 0 to `t` of ``2 * pi * f(t)``,
+    ``f(t)`` as defined above.
+
+    Examples
+    --------
+    Compute the waveform with instantaneous frequency::
+
+        f(t) = 0.025*t**3 - 0.36*t**2 + 1.25*t + 2
+
+    over the interval 0 <= t <= 10.
+
+    >>> import numpy as np
+    >>> from scipy.signal import sweep_poly
+    >>> p = np.poly1d([0.025, -0.36, 1.25, 2.0])
+    >>> t = np.linspace(0, 10, 5001)
+    >>> w = sweep_poly(t, p)
+
+    Plot it:
+
+    >>> import matplotlib.pyplot as plt
+    >>> plt.subplot(2, 1, 1)
+    >>> plt.plot(t, w)
+    >>> plt.title("Sweep Poly\\nwith frequency " +
+    ...           "$f(t) = 0.025t^3 - 0.36t^2 + 1.25t + 2$")
+    >>> plt.subplot(2, 1, 2)
+    >>> plt.plot(t, p(t), 'r', label='f(t)')
+    >>> plt.legend()
+    >>> plt.xlabel('t')
+    >>> plt.tight_layout()
+    >>> plt.show()
+
+    """
+    # 'phase' is computed in _sweep_poly_phase, to make testing easier.
+    phase = _sweep_poly_phase(t, poly)
+    # Convert to radians.
+    phi *= pi / 180
+    return cos(phase + phi)
+
+
+def _sweep_poly_phase(t, poly):
+    """
+    Calculate the phase used by sweep_poly to generate its output.
+
+    See `sweep_poly` for a description of the arguments.
+
+    """
+    # polyint handles lists, ndarrays and instances of poly1d automatically.
+    intpoly = polyint(poly)
+    phase = 2 * pi * polyval(intpoly, t)
+    return phase
+
+
+def unit_impulse(shape, idx=None, dtype=float):
+    r"""
+    Unit impulse signal (discrete delta function) or unit basis vector.
+
+    Parameters
+    ----------
+    shape : int or tuple of int
+        Number of samples in the output (1-D), or a tuple that represents the
+        shape of the output (N-D).
+    idx : None or int or tuple of int or 'mid', optional
+        Index at which the value is 1.  If None, defaults to the 0th element.
+        If ``idx='mid'``, the impulse will be centered at ``shape // 2`` in
+        all dimensions.  If an int, the impulse will be at `idx` in all
+        dimensions.
+    dtype : data-type, optional
+        The desired data-type for the array, e.g., ``numpy.int8``.  Default is
+        ``numpy.float64``.
+
+    Returns
+    -------
+    y : ndarray
+        Output array containing an impulse signal.
+
+    Notes
+    -----
+    In digital signal processing literature the unit impulse signal is often
+    represented by the Kronecker delta. [1]_ I.e., a signal :math:`u_k[n]`,
+    which is zero everywhere except being one at the :math:`k`-th sample,
+    can be expressed as
+
+    .. math::
+
+        u_k[n] = \delta[n-k] \equiv \delta_{n,k}\ .
+
+    Furthermore, the unit impulse is frequently interpreted as the discrete-time
+    version of the continuous-time Dirac distribution. [2]_
+
+    References
+    ----------
+    .. [1] "Kronecker delta", *Wikipedia*,
+           https://en.wikipedia.org/wiki/Kronecker_delta#Digital_signal_processing
+    .. [2] "Dirac delta function" *Wikipedia*,
+           https://en.wikipedia.org/wiki/Dirac_delta_function#Relationship_to_the_Kronecker_delta
+
+    .. versionadded:: 0.19.0
+
+    Examples
+    --------
+    An impulse at the 0th element (:math:`\\delta[n]`):
+
+    >>> from scipy import signal
+    >>> signal.unit_impulse(8)
+    array([ 1.,  0.,  0.,  0.,  0.,  0.,  0.,  0.])
+
+    Impulse offset by 2 samples (:math:`\\delta[n-2]`):
+
+    >>> signal.unit_impulse(7, 2)
+    array([ 0.,  0.,  1.,  0.,  0.,  0.,  0.])
+
+    2-dimensional impulse, centered:
+
+    >>> signal.unit_impulse((3, 3), 'mid')
+    array([[ 0.,  0.,  0.],
+           [ 0.,  1.,  0.],
+           [ 0.,  0.,  0.]])
+
+    Impulse at (2, 2), using broadcasting:
+
+    >>> signal.unit_impulse((4, 4), 2)
+    array([[ 0.,  0.,  0.,  0.],
+           [ 0.,  0.,  0.,  0.],
+           [ 0.,  0.,  1.,  0.],
+           [ 0.,  0.,  0.,  0.]])
+
+    Plot the impulse response of a 4th-order Butterworth lowpass filter:
+
+    >>> imp = signal.unit_impulse(100, 'mid')
+    >>> b, a = signal.butter(4, 0.2)
+    >>> response = signal.lfilter(b, a, imp)
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> plt.plot(np.arange(-50, 50), imp)
+    >>> plt.plot(np.arange(-50, 50), response)
+    >>> plt.margins(0.1, 0.1)
+    >>> plt.xlabel('Time [samples]')
+    >>> plt.ylabel('Amplitude')
+    >>> plt.grid(True)
+    >>> plt.show()
+
+    """
+    out = zeros(shape, dtype)
+
+    shape = np.atleast_1d(shape)
+
+    if idx is None:
+        idx = (0,) * len(shape)
+    elif idx == 'mid':
+        idx = tuple(shape // 2)
+    elif not hasattr(idx, "__iter__"):
+        idx = (idx,) * len(shape)
+
+    out[idx] = 1
+    return out

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/_wavelets.py

@@ -0,0 +1,29 @@
+import numpy as np
+from scipy.signal import convolve
+
+
+def _ricker(points, a):
+    A = 2 / (np.sqrt(3 * a) * (np.pi**0.25))
+    wsq = a**2
+    vec = np.arange(0, points) - (points - 1.0) / 2
+    xsq = vec**2
+    mod = (1 - xsq / wsq)
+    gauss = np.exp(-xsq / (2 * wsq))
+    total = A * mod * gauss
+    return total
+
+
+def _cwt(data, wavelet, widths, dtype=None, **kwargs):
+    # Determine output type
+    if dtype is None:
+        if np.asarray(wavelet(1, widths[0], **kwargs)).dtype.char in 'FDG':
+            dtype = np.complex128
+        else:
+            dtype = np.float64
+
+    output = np.empty((len(widths), len(data)), dtype=dtype)
+    for ind, width in enumerate(widths):
+        N = np.min([10 * width, len(data)])
+        wavelet_data = np.conj(wavelet(N, width, **kwargs)[::-1])
+        output[ind] = convolve(data, wavelet_data, mode='same')
+    return output

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/bsplines.py

@@ -0,0 +1,21 @@
+# This file is not meant for public use and will be removed in SciPy v2.0.0.
+# Use the `scipy.signal` namespace for importing the functions
+# included below.
+
+from scipy._lib.deprecation import _sub_module_deprecation
+
+__all__ = [  # noqa: F822
+    'spline_filter', 'gauss_spline',
+    'cspline1d', 'qspline1d', 'cspline1d_eval', 'qspline1d_eval',
+    'cspline2d', 'sepfir2d'
+]
+
+
+def __dir__():
+    return __all__
+
+
+def __getattr__(name):
+    return _sub_module_deprecation(sub_package="signal", module="bsplines",
+                                   private_modules=["_spline_filters"], all=__all__,
+                                   attribute=name)

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/filter_design.py

@@ -0,0 +1,28 @@
+# This file is not meant for public use and will be removed in SciPy v2.0.0.
+# Use the `scipy.signal` namespace for importing the functions
+# included below.
+
+from scipy._lib.deprecation import _sub_module_deprecation
+
+__all__ = [  # noqa: F822
+    'findfreqs', 'freqs', 'freqz', 'tf2zpk', 'zpk2tf', 'normalize',
+    'lp2lp', 'lp2hp', 'lp2bp', 'lp2bs', 'bilinear', 'iirdesign',
+    'iirfilter', 'butter', 'cheby1', 'cheby2', 'ellip', 'bessel',
+    'band_stop_obj', 'buttord', 'cheb1ord', 'cheb2ord', 'ellipord',
+    'buttap', 'cheb1ap', 'cheb2ap', 'ellipap', 'besselap',
+    'BadCoefficients', 'freqs_zpk', 'freqz_zpk',
+    'tf2sos', 'sos2tf', 'zpk2sos', 'sos2zpk', 'group_delay',
+    'sosfreqz', 'freqz_sos', 'iirnotch', 'iirpeak', 'bilinear_zpk',
+    'lp2lp_zpk', 'lp2hp_zpk', 'lp2bp_zpk', 'lp2bs_zpk',
+    'gammatone', 'iircomb',
+]
+
+
+def __dir__():
+    return __all__
+
+
+def __getattr__(name):
+    return _sub_module_deprecation(sub_package="signal", module="filter_design",
+                                   private_modules=["_filter_design"], all=__all__,
+                                   attribute=name)

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/fir_filter_design.py

@@ -0,0 +1,20 @@
+# This file is not meant for public use and will be removed in SciPy v2.0.0.
+# Use the `scipy.signal` namespace for importing the functions
+# included below.
+
+from scipy._lib.deprecation import _sub_module_deprecation
+
+__all__ = [  # noqa: F822
+    'kaiser_beta', 'kaiser_atten', 'kaiserord',
+    'firwin', 'firwin2', 'remez', 'firls', 'minimum_phase',
+]
+
+
+def __dir__():
+    return __all__
+
+
+def __getattr__(name):
+    return _sub_module_deprecation(sub_package="signal", module="fir_filter_design",
+                                   private_modules=["_fir_filter_design"], all=__all__,
+                                   attribute=name)

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/lti_conversion.py

@@ -0,0 +1,20 @@
+# This file is not meant for public use and will be removed in SciPy v2.0.0.
+# Use the `scipy.signal` namespace for importing the functions
+# included below.
+
+from scipy._lib.deprecation import _sub_module_deprecation
+
+__all__ = [  # noqa: F822
+    'tf2ss', 'abcd_normalize', 'ss2tf', 'zpk2ss', 'ss2zpk',
+    'cont2discrete', 'tf2zpk', 'zpk2tf', 'normalize'
+]
+
+
+def __dir__():
+    return __all__
+
+
+def __getattr__(name):
+    return _sub_module_deprecation(sub_package="signal", module="lti_conversion",
+                                   private_modules=["_lti_conversion"], all=__all__,
+                                   attribute=name)

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/ltisys.py

@@ -0,0 +1,25 @@
+# This file is not meant for public use and will be removed in SciPy v2.0.0.
+# Use the `scipy.signal` namespace for importing the functions
+# included below.
+
+from scipy._lib.deprecation import _sub_module_deprecation
+
+__all__ = [  # noqa: F822
+    'lti', 'dlti', 'TransferFunction', 'ZerosPolesGain', 'StateSpace',
+    'lsim', 'impulse', 'step', 'bode',
+    'freqresp', 'place_poles', 'dlsim', 'dstep', 'dimpulse',
+    'dfreqresp', 'dbode',
+    'tf2zpk', 'zpk2tf', 'normalize', 'freqs',
+    'freqz', 'freqs_zpk', 'freqz_zpk', 'tf2ss', 'abcd_normalize',
+    'ss2tf', 'zpk2ss', 'ss2zpk', 'cont2discrete',
+]
+
+
+def __dir__():
+    return __all__
+
+
+def __getattr__(name):
+    return _sub_module_deprecation(sub_package="signal", module="ltisys",
+                                   private_modules=["_ltisys"], all=__all__,
+                                   attribute=name)

infer_4_30_0/lib/python3.10/site-packages/scipy/signal/signaltools.py

@@ -0,0 +1,27 @@
+# This file is not meant for public use and will be removed in SciPy v2.0.0.
+# Use the `scipy.signal` namespace for importing the functions
+# included below.
+
+from scipy._lib.deprecation import _sub_module_deprecation
+
+__all__ = [  # noqa: F822
+    'correlate', 'correlation_lags', 'correlate2d',
+    'convolve', 'convolve2d', 'fftconvolve', 'oaconvolve',
+    'order_filter', 'medfilt', 'medfilt2d', 'wiener', 'lfilter',
+    'lfiltic', 'sosfilt', 'deconvolve', 'hilbert', 'hilbert2',
+    'unique_roots', 'invres', 'invresz', 'residue',
+    'residuez', 'resample', 'resample_poly', 'detrend',
+    'lfilter_zi', 'sosfilt_zi', 'sosfiltfilt', 'choose_conv_method',
+    'filtfilt', 'decimate', 'vectorstrength',
+    'dlti', 'upfirdn', 'get_window', 'cheby1', 'firwin'
+]
+
+
+def __dir__():
+    return __all__
+
+
+def __getattr__(name):
+    return _sub_module_deprecation(sub_package="signal", module="signaltools",
+                                   private_modules=["_signaltools"], all=__all__,
+                                   attribute=name)