matplotlib.pyplot.pcolormesh

matplotlib.pyplot.pcolormesh(*args, alpha=None, norm=None, cmap=None, vmin=None, vmax=None, shading='flat', antialiased=False, data=None, **kwargs) [source]

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

Call signature:

pcolor([X, Y,] C, **kwargs)

X and Y can be used to specify the corners of the quadrilaterals.

Note

pcolormesh() is similar to pcolor(). It's much faster and preferred in most cases. For a detailed discussion on the differences see Differences between pcolor() and pcolormesh().

Parameters:	C : array_like A scalar 2-D array. The values will be color-mapped. X, Y : array_like, optional The coordinates of the quadrilateral corners. The quadrilateral for C[i,j] has corners at: (X[i+1, j], Y[i+1, j]) (X[i+1, j+1], Y[i+1, j+1]) +--------+ | C[i,j] | +--------+ (X[i, j], Y[i, j]) (X[i, j+1], Y[i, j+1]), Note that the column index corresponds to the x-coordinate, and the row index corresponds to y. For details, see the Notes section below. The dimensions of X and Y should be one greater than those of C. Alternatively, X, Y and C may have equal dimensions, in which case the last row and column of C will be ignored. If X and/or Y are 1-D arrays or column vectors they will be expanded as needed into the appropriate 2-D arrays, making a rectangular grid. 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). edgecolors : {'none', None, 'face', color, color sequence}, optional The color of the edges. Defaults to 'none'. Possible values: 'none' or '': No edge. None: rcParams["patch.edgecolor"] will be used. Note that currently rcParams["patch.force_edgecolor"] has to be True for this to work. 'face': Use the adjacent face color. An mpl color or sequence of colors will set the edge color. The singular form edgecolor works as an alias. alpha : scalar, optional, default: None The alpha blending value, between 0 (transparent) and 1 (opaque). shading : {'flat', 'gouraud'}, optional The fill style, Possible values: 'flat': A solid color is used for each quad. The color of the quad (i, j), (i+1, j), (i, j+1), (i+1, j+1) is given by C[i,j]. 'gouraud': Each quad will be Gouraud shaded: The color of the corners (i', j') are given by C[i',j']. The color values of the area in between is interpolated from the corner values. When Gouraud shading is used, edgecolors is ignored. snap : bool, optional, default: False Whether to snap the mesh to pixel boundaries.
Returns:	mesh : matplotlib.collections.QuadMesh
Other Parameters:	**kwargs Additionally, the following arguments are allowed. They are passed along to the QuadMesh constructor: Property Description agg_filter a filter function, which takes a (m, n, 3) float array and a dpi value, and returns a (m, n, 3) array alpha float or None animated bool antialiased or aa or antialiaseds bool or sequence of bools array ndarray capstyle {'butt', 'round', 'projecting'} clim a length 2 sequence of floats; may be overridden in methods that have vmin and vmax kwargs. clip_box Bbox clip_on bool clip_path [(Path, Transform) | Patch | None] cmap colormap or registered colormap name color color or sequence of rgba tuples contains callable edgecolor or ec or edgecolors color or sequence of colors or 'face' facecolor or facecolors or fc color or sequence of colors figure Figure gid str hatch {'/', '\', '|', '-', '+', 'x', 'o', 'O', '.', '*'} in_layout bool joinstyle {'miter', 'round', 'bevel'} label object linestyle or dashes or linestyles or ls {'-', '--', '-.', ':', '', (offset, on-off-seq), ...} linewidth or linewidths or lw float or sequence of floats norm Normalize offset_position {'screen', 'data'} offsets float or sequence of floats path_effects AbstractPathEffect picker None or bool or float or callable pickradius unknown rasterized bool or None sketch_params (scale: float, length: float, randomness: float) snap bool or None transform Transform url str urls List[str] or None visible bool zorder float

See also

pcolor

An alternative implementation with slightly different features. For a detailed discussion on the differences see Differences between pcolor() and pcolormesh().

imshow

If X and Y are each equidistant, imshow can be a faster alternative.

Notes

Masked arrays

C may be a masked array. If C[i, j] is masked, the corresponding quadrilateral will be transparent. Masking of X and Y is not supported. Use pcolor if you need this functionality.

Grid orientation

The grid orientation follows the standard matrix convention: An array C with shape (nrows, ncolumns) is plotted with the column number as X and the row number as Y.

Differences between pcolor() and pcolormesh()

Both methods are used to create a pseudocolor plot of a 2-D array using quadrilaterals.

The main difference lies in the created object and internal data handling: While pcolor returns a PolyCollection, pcolormesh returns a QuadMesh. The latter is more specialized for the given purpose and thus is faster. It should almost always be preferred.

There is also a slight difference in the handling of masked arrays. Both pcolor and pcolormesh support masked arrays for C. However, only pcolor supports masked arrays for X and Y. The reason lies in the internal handling of the masked values. pcolor leaves out the respective polygons from the PolyCollection. pcolormesh sets the facecolor of the masked elements to transparent. You can see the difference when using edgecolors. While all edges are drawn irrespective of masking in a QuadMesh, the edge between two adjacent masked quadrilaterals in pcolor is not drawn as the corresponding polygons do not exist in the PolyCollection.

Another difference is the support of Gouraud shading in pcolormesh, which is not available with pcolor.

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).

Examples using matplotlib.pyplot.pcolormesh