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# matplotlib.axes.Axes.pcolorfast¶

`Axes.``pcolorfast`(*args, alpha=None, norm=None, cmap=None, vmin=None, vmax=None, data=None, **kwargs)[source]

Create a pseudocolor plot with a non-regular rectangular grid.

Call signatures:

```ax.pcolorfast(C, **kwargs)
ax.pcolorfast(xr, yr, C, **kwargs)
ax.pcolorfast(x, y, C, **kwargs)
ax.pcolorfast(X, Y, C, **kwargs)
```

This method is similar to ~.Axes.pcolor` and `pcolormesh`. It's designed to provide the fastest pcolor-type plotting with the Agg backend. To achieve this, it uses different algorithms internally depending on the complexity of the input grid (regular rectangular, non-regular rectangular or arbitrary quadrilateral).

Warning

This method is experimental. Compared to `pcolor` or `pcolormesh` it has some limitations:

• It supports only flat shading (no outlines)
• It lacks support for log scaling of the axes.
• It does not have a have a pyplot wrapper.
Parameters: C : array-like(M, N) A scalar 2D array. The values will be color-mapped. C may be a masked array. x, y : tuple or array-like X and Y are used to specify the coordinates of the quadilaterals. There are different ways to do this: Use tuples `xr=(xmin, xmax)` and `yr=(ymin, ymax)` to define a uniform rectiangular grid. The tuples define the outer edges of the grid. All individual quadrilaterals will be of the same size. This is the fastest version. Use 1D arrays x, y to specify a non-uniform rectangular grid. In this case x and y have to be monotonic 1D arrays of length N+1 and M+1, specifying the x and y boundaries of the cells. The speed is intermediate. Note: The grid is checked, and if found to be uniform the fast version is used. Use 2D arrays X, Y if you need an arbitrary quadrilateral grid (i.e. if the quadrilaterals are not rectangular). In this case X and Y are 2D arrays with shape (M, N), specifying the x and y coordinates of the corners of the colored quadrilaterals. See `pcolormesh` for details. This is the most general, but the slowest to render. It may produce faster and more compact output using ps, pdf, and svg backends, however. Leaving out x and y defaults to `xr=(0, N)`, `yr=(O, M)`. cmap : str or `Colormap`, optional A Colormap instance or registered colormap name. The colormap maps the C values to colors. Defaults to `rcParams["image.cmap"]`. norm : `Normalize`, optional The Normalize instance scales the data values to the canonical colormap range [0, 1] for mapping to colors. By default, the data range is mapped to the colorbar range using linear scaling. vmin, vmax : scalar, optional, default: None The colorbar range. If None, suitable min/max values are automatically chosen by the `Normalize` instance (defaults to the respective min/max values of C in case of the default linear scaling). alpha : scalar, optional, default: None The alpha blending value, between 0 (transparent) and 1 (opaque). snap : bool, optional, default: False Whether to snap the mesh to pixel boundaries. image : The return type depends on the type of grid: `AxesImage` for a regular rectangular grid. `PcolorImage` for a non-regular rectangular grid. `QuadMesh` for a non-rectangular grid.

Notes

Note

In addition to the above described arguments, this function can take a data keyword argument. If such a data argument is given, the following arguments are replaced by data[<arg>]:

• All positional and all keyword arguments.

Objects passed as data must support item access (`data[<arg>]`) and membership test (`<arg> in data`).