pandas.Series.interpolate   Series.interpolate(method='linear', axis=0, limit=None, inplace=False, limit_direction=None, limit_area=None, downcast=None, **kwargs)[source]
 
Fill NaN values using an interpolation method. Please note that only method='linear' is supported for DataFrame/Series with a MultiIndex.  Parameters 
 
method:str, default ‘linear’


Interpolation technique to use. One of:  ‘linear’: Ignore the index and treat the values as equally spaced. This is the only method supported on MultiIndexes. ‘time’: Works on daily and higher resolution data to interpolate given length of interval. ‘index’, ‘values’: use the actual numerical values of the index. ‘pad’: Fill in NaNs using existing values. ‘nearest’, ‘zero’, ‘slinear’, ‘quadratic’, ‘cubic’, ‘spline’, ‘barycentric’, ‘polynomial’: Passed to scipy.interpolate.interp1d. These methods use the numerical values of the index. Both ‘polynomial’ and ‘spline’ require that you also specify an order (int), e.g. df.interpolate(method='polynomial', order=5). ‘krogh’, ‘piecewise_polynomial’, ‘spline’, ‘pchip’, ‘akima’, ‘cubicspline’: Wrappers around the SciPy interpolation methods of similar names. See Notes. ‘from_derivatives’: Refers to scipy.interpolate.BPoly.from_derivatives which replaces ‘piecewise_polynomial’ interpolation method in scipy 0.18.   
axis:{{0 or ‘index’, 1 or ‘columns’, None}}, default None


Axis to interpolate along.  
limit:int, optional


Maximum number of consecutive NaNs to fill. Must be greater than 0.  
inplace:bool, default False


Update the data in place if possible.  
limit_direction:{{‘forward’, ‘backward’, ‘both’}}, Optional


Consecutive NaNs will be filled in this direction.  If limit is specified:

 If ‘method’ is ‘pad’ or ‘ffill’, ‘limit_direction’ must be ‘forward’. If ‘method’ is ‘backfill’ or ‘bfill’, ‘limit_direction’ must be ‘backwards’.   If ‘limit’ is not specified:

 If ‘method’ is ‘backfill’ or ‘bfill’, the default is ‘backward’ else the default is ‘forward’     Changed in version 1.1.0: raises ValueError if limit_direction is ‘forward’ or ‘both’ and method is ‘backfill’ or ‘bfill’. raises ValueError if limit_direction is ‘backward’ or ‘both’ and method is ‘pad’ or ‘ffill’.   
limit_area:{{None, ‘inside’, ‘outside’}}, default None


If limit is specified, consecutive NaNs will be filled with this restriction.  None: No fill restriction. ‘inside’: Only fill NaNs surrounded by valid values (interpolate). ‘outside’: Only fill NaNs outside valid values (extrapolate).   
downcast:optional, ‘infer’ or None, defaults to None


Downcast dtypes if possible.  
``**kwargs``:optional


Keyword arguments to pass on to the interpolating function.    Returns 
 Series or DataFrame or None

Returns the same object type as the caller, interpolated at some or all NaN values or None if inplace=True.      See also  fillna

Fill missing values using different methods.  scipy.interpolate.Akima1DInterpolator

Piecewise cubic polynomials (Akima interpolator).  scipy.interpolate.BPoly.from_derivatives

Piecewise polynomial in the Bernstein basis.  scipy.interpolate.interp1d

Interpolate a 1-D function.  scipy.interpolate.KroghInterpolator

Interpolate polynomial (Krogh interpolator).  scipy.interpolate.PchipInterpolator

PCHIP 1-d monotonic cubic interpolation.  scipy.interpolate.CubicSpline

Cubic spline data interpolator.    Notes The ‘krogh’, ‘piecewise_polynomial’, ‘spline’, ‘pchip’ and ‘akima’ methods are wrappers around the respective SciPy implementations of similar names. These use the actual numerical values of the index. For more information on their behavior, see the SciPy documentation and SciPy tutorial. Examples Filling in NaN in a Series via linear interpolation. 
>>> s = pd.Series([0, 1, np.nan, 3])
>>> s
0    0.0
1    1.0
2    NaN
3    3.0
dtype: float64
>>> s.interpolate()
0    0.0
1    1.0
2    2.0
3    3.0
dtype: float64
  Filling in NaN in a Series by padding, but filling at most two consecutive NaN at a time. 
>>> s = pd.Series([np.nan, "single_one", np.nan,
...                "fill_two_more", np.nan, np.nan, np.nan,
...                4.71, np.nan])
>>> s
0              NaN
1       single_one
2              NaN
3    fill_two_more
4              NaN
5              NaN
6              NaN
7             4.71
8              NaN
dtype: object
>>> s.interpolate(method='pad', limit=2)
0              NaN
1       single_one
2       single_one
3    fill_two_more
4    fill_two_more
5    fill_two_more
6              NaN
7             4.71
8             4.71
dtype: object
  Filling in NaN in a Series via polynomial interpolation or splines: Both ‘polynomial’ and ‘spline’ methods require that you also specify an order (int). 
>>> s = pd.Series([0, 2, np.nan, 8])
>>> s.interpolate(method='polynomial', order=2)
0    0.000000
1    2.000000
2    4.666667
3    8.000000
dtype: float64
  Fill the DataFrame forward (that is, going down) along each column using linear interpolation. Note how the last entry in column ‘a’ is interpolated differently, because there is no entry after it to use for interpolation. Note how the first entry in column ‘b’ remains NaN, because there is no entry before it to use for interpolation. 
>>> df = pd.DataFrame([(0.0, np.nan, -1.0, 1.0),
...                    (np.nan, 2.0, np.nan, np.nan),
...                    (2.0, 3.0, np.nan, 9.0),
...                    (np.nan, 4.0, -4.0, 16.0)],
...                   columns=list('abcd'))
>>> df
     a    b    c     d
0  0.0  NaN -1.0   1.0
1  NaN  2.0  NaN   NaN
2  2.0  3.0  NaN   9.0
3  NaN  4.0 -4.0  16.0
>>> df.interpolate(method='linear', limit_direction='forward', axis=0)
     a    b    c     d
0  0.0  NaN -1.0   1.0
1  1.0  2.0 -2.0   5.0
2  2.0  3.0 -3.0   9.0
3  2.0  4.0 -4.0  16.0
  Using polynomial interpolation. 
>>> df['d'].interpolate(method='polynomial', order=2)
0     1.0
1     4.0
2     9.0
3    16.0
Name: d, dtype: float64