Axes.pcolor(self, *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.


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.

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'}, optional

The fill style for the quadrilateral; defaults to 'flat' or rcParams["pcolor.shading"] (default: 'flat'). 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 deprecated 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:

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.

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.


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 ndarray 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
contains unknown
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_position unknown
offsets (N, 2) or (2,) array-like
path_effects AbstractPathEffect
picker None or bool or float or callable
pickradius float
rasterized bool
sketch_params (scale: float, length: float, randomness: float)
snap bool or None
transform Transform
url str
urls list of str or None
visible bool
zorder float

See also

for an explanation of the differences between pcolor and pcolormesh.
If X and Y are each equidistant, imshow can be a faster alternative.


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.


In addition to the above described arguments, this function can take a data keyword argument. If such a data argument is given, every other argument can also be string s, which is interpreted as data[s] (unless this raises an exception).

Objects passed as data must support item access (data[s]) and membership test (s in data).