matplotlib.axes.Axes.pcolor

Axes.pcolor(*args, shading=None, 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 signature:

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

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

Hint

pcolor() can be very slow for large arrays. In most cases you should use the similar but much faster pcolormesh instead. See Differences between pcolor() and pcolormesh() for a discussion of the differences.

Parameters

C2D array-like

The color-mapped values.

X, Yarray-like, optional

The coordinates of the corners of quadrilaterals of a pcolormesh:

(X[i+1, j], Y[i+1, j])       (X[i+1, j+1], Y[i+1, j+1])
                      +-----+
                      |     |
                      +-----+
    (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.

If shading='flat' the dimensions of X and Y should be one greater than those of C, and the quadrilateral is colored due to the value at C[i, j]. If X, Y and C have equal dimensions, a warning will be raised and the last row and column of C will be ignored.

If shading='nearest', the dimensions of X and Y should be the same as those of C (if not, a ValueError will be raised). The color C[i, j] will be centered on (X[i, j], Y[i, j]).

If X and/or Y are 1-D arrays or column vectors they will be expanded as needed into the appropriate 2D arrays, making a rectangular grid.

shading{'flat', 'nearest', 'auto'}, default: rcParams["pcolor.shading"] (default: 'auto')

The fill style for the quadrilateral. 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]. The dimensions of X and Y should be one greater than those of C; if they are the same as C, then a deprecation warning is raised, and the last row and column of C are dropped.
• 'nearest': Each grid point will have a color centered on it, extending halfway between the adjacent grid centers. The dimensions of X and Y must be the same as C.
• 'auto': Choose 'flat' if dimensions of X and Y are one larger than C. Choose 'nearest' if dimensions are the same.

See pcolormesh grids and shading for more description.

cmapstr or Colormap, default: rcParams["image.cmap"] (default: 'viridis')

A Colormap instance or registered colormap name. The colormap maps the C values to colors.

normNormalize, 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, vmaxfloat, 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). It is an error to use vmin/vmax when norm is given.

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"] (default: 'black') will be used. Note that currently rcParams["patch.force_edgecolor"] (default: False) has to be True for this to work.
• 'face': Use the adjacent face color.
• A color or sequence of colors will set the edge color.

The singular form edgecolor works as an alias.

alphafloat, default: None

The alpha blending value of the face color, between 0 (transparent) and 1 (opaque). Note: The edgecolor is currently not affected by this.

snapbool, default: False

Whether to snap the mesh to pixel boundaries.

Returns

matplotlib.collections.Collection

Other Parameters

antialiasedsbool, default: False

The default antialiaseds is False if the default edgecolors="none" is used. This eliminates artificial lines at patch boundaries, and works regardless of the value of alpha. If edgecolors is not "none", then the default antialiaseds is taken from rcParams["patch.antialiased"] (default: True). Stroking the edges may be preferred if alpha is 1, but will cause artifacts otherwise.

dataindexable object, optional

If given, all parameters also accept a string s, which is interpreted as data[s] (unless this raises an exception).

**kwargs

Additionally, the following arguments are allowed. They are passed along to the PolyCollection 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	array-like or scalar or None
animated	bool
antialiased or aa or antialiaseds	bool or list of bools
array	array-like or None
capstyle	CapStyle or {'butt', 'projecting', 'round'}
clim	(vmin: float, vmax: float)
clip_box	Bbox
clip_on	bool
clip_path	Patch or (Path, Transform) or None
cmap	Colormap or str or None
color	color or list of rgba tuples
edgecolor or ec or edgecolors	color or list of colors or 'face'
facecolor or facecolors or fc	color or list of colors
figure	Figure
gid	str
hatch	{'/', '\', '|', '-', '+', 'x', 'o', 'O', '.', '*'}
in_layout	bool
joinstyle	JoinStyle or {'miter', 'round', 'bevel'}
label	object
linestyle or dashes or linestyles or ls	str or tuple or list thereof
linewidth or linewidths or lw	float or list of floats
norm	Normalize or None
offset_transform	Transform
offsets	(N, 2) or (2,) array-like
path_effects	AbstractPathEffect
paths	list of array-like
picker	None or bool or float or callable
pickradius	float
rasterized	bool
sizes	ndarray or None
sketch_params	(scale: float, length: float, randomness: float)
snap	bool or None
transform	Transform
url	str
urls	list of str or None
verts	list of array-like
verts_and_codes	unknown
visible	bool
zorder	float

See also

pcolormesh

for an explanation of the differences between pcolor and pcolormesh.

imshow

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

Notes

Masked arrays

X, Y and C may be masked arrays. If either C[i, j], or one of the vertices surrounding C[i, j] (X or Y at [i, j], [i+1, j], [i, j+1], [i+1, j+1]) is masked, nothing is plotted.

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.

Examples using matplotlib.axes.Axes.pcolor