matspy 1.0.0
Sparse matrix spy plot and sparkline renderer that works with Jupyter.
Requires Python: >=3.7
Keywords: matrix,sparse,spy,plot,graph,numpy,scipy,graphblas

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# MatSpy

Sparse matrix spy plot and sparkline renderer.

```python
from matspy import spy

spy(A)
```

<img src="https://raw.githubusercontent.com/alugowski/matspy/main/doc/images/spy.png" width="400" alt="Spy Plot"/>

Supports:
* **SciPy** - sparse matrices and arrays like `csr_matrix` and `coo_array` [(https://nbviewer.org/github/alugowski/matspy/blob/main/demo)](https://nbviewer.org/github/alugowski/matspy/blob/main/demo.ipynb)
* **NumPy** - `ndarray` [(https://nbviewer.org/github/alugowski/matspy/blob/main/demo)](https://nbviewer.org/github/alugowski/matspy/blob/main/demo-numpy.ipynb)
* **[Python-graphblas](https://github.com/python-graphblas/python-graphblas)** - `gb.Matrix` [(https://nbviewer.org/github/alugowski/matspy/blob/main/demo)](https://nbviewer.org/github/alugowski/matspy/blob/main/demo-python-graphblas.ipynb)
* **[PyData/Sparse](https://sparse.pydata.org/)** - `COO`, `DOK`, `GCXS`  [(https://nbviewer.org/github/alugowski/matspy/blob/main/demo)](https://nbviewer.org/github/alugowski/matspy/blob/main/demo-pydata-sparse.ipynb)

Features:
* Simple `spy()` method plots non-zero structure of a matrix, similar to MatLAB's spy.
* Sparklines: `to_sparkline()` creates small self-contained spy plots for inline HTML visuals.
* FAST and handles very large matrices.

See a [Jupyter notebook demo](https://nbviewer.org/github/alugowski/matspy/blob/main/demo.ipynb).

```shell
pip install matspy
```
```shell
conda install matspy
 ```

## Methods
* `spy(A)`: Plot the sparsity pattern (location of nonzero values) of sparse matrix `A`.
* `to_sparkline(A)`: Return a small spy plot as a self-contained HTML string. Multiple sparklines can be automatically to-scale with each other using the `retscale` and `scale` arguments.
* `spy_to_mpl(A)`: Same as `spy()` but returns the matplotlib Figure without showing it.
* `to_spy_heatmap(A)`: Return the raw 2D array for spy plots. 

## Examples

See the [demo notebook](https://nbviewer.org/github/alugowski/matspy/blob/main/demo.ipynb) for more.

#### Save spy plot as a PNG image

```python
fig, ax = matspy.spy_to_mpl(A)
fig.savefig("spy.png", bbox_inches='tight')
```

## Arguments

All methods take the same arguments. Apart from the matrix itself:

* `title`: string label. If `True`, then a matrix description is auto generated.
* `indices`: Whether to show matrix indices.
* `figsize`, `sparkline_size`: size of the plot, in inches
* `shading`: `binary`, `relative`, `absolute`.
* `buckets`: spy plot pixels (longest side).
* `dpi`: determine `buckets` relative to figure size.
* `precision`: For numpy arrays, only plot values with magnitude greater than `precision`. Like [matplotlib.pyplot.spy()](https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.spy.html)'s `precision`.

### Overriding defaults
`matspy.params` contains the default values for all arguments.

For example, to default to binary shading, no title, and no indices:

```python
matspy.params.shading = 'binary'
matspy.params.title = False
matspy.params.indices = False
```

## Jupyter

`spy()` simply shows a matplotlib figure and works well within Jupyter.

`to_sparkline()` creates small spy plots that work anywhere HTML is displayed.

# Fast
All operations work with very large matrices.
A spy plot of tens of millions of elements takes less than half a second.

Large matrices are downscaled using two native matrix multiplies. The final dense 2D image is small.

<img src="https://raw.githubusercontent.com/alugowski/matspy/main/doc/images/triple_product.png" height="125" width="400" alt="triple product"/>

Note: the spy plots in this image were created with `to_sparkline()`. Code in the [demo notebook](https://nbviewer.org/github/alugowski/matspy/blob/main/demo.ipynb).

# Spy Plot Anti-Aliasing
One application of spy plots is to quickly see if a matrix has a noticeable structure.
Aliasing artifacts can give the false impression of structure where none exists,
such as moiré or even a false grid pattern.

MatSpy employs some simple methods to help eliminate these effects in most cases.

![sparkline AA](https://raw.githubusercontent.com/alugowski/matspy/main/doc/images/sparkline_aa.png)

See the [Anti-Aliasing demo](https://nbviewer.org/github/alugowski/matspy/blob/main/demo-anti-aliasing.ipynb) for more.

# How to support more packages

Each package that MatSpy supports implements two classes:

* `Driver`: Declares what types are supported and supplies an adapter.
  * `get_supported_type_prefixes`: This declares what types are supported, as strings to avoid unnecessary imports.
  * `adapt_spy(A)`: Returns a `MatrixSpyAdapter` for a matrix that this driver supports.
* `MatrixSpyAdapter`. A common interface for extracting spy data.
  * `describe()`: Describes the adapted matrix. This description serves as the plot title.
  * `get_shape()`: Returns the adapted matrix's shape.
  * `get_spy()`: Returns spy plot data as a dense 2D numpy array.

See [matspy/adapters](matspy/adapters) for details.

You may use `matspy.register_driver` to register a `Driver` for your own matrix class.