matplotlib.axes.Axes.pcolor

Axes.pcolor(*args, data=None, **kwargs)

Create a pseudocolor plot of a 2-D array.

Call signatures:

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

pcolor can be very slow for large arrays; consider using the similar but much faster pcolormesh() instead.

Parameters:

C : array_like

An array of color values.

X, Y : array_like, optional

If given, specify the (x, y) coordinates of the colored quadrilaterals; the quadrilateral for C[i,j] has corners at:

(X[i,   j],   Y[i,   j]),
(X[i,   j+1], Y[i,   j+1]),
(X[i+1, j],   Y[i+1, j]),
(X[i+1, j+1], Y[i+1, j+1])

Ideally the dimensions of X and Y should be one greater than those of C; if the dimensions are the same, then the last row and column of C will be ignored.

Note that the column index corresponds to the x-coordinate, and the row index corresponds to y; for details, see the Grid Orientation section below.

If either or both of X and 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 : Colormap, optional, default: None

If None, default to rc settings.

norm : matplotlib.colors.Normalize, optional, default: None

An instance is used to scale luminance data to (0, 1). If None, defaults to normalize().

vmin, vmax : scalar, optional, default: None

vmin and vmax are used in conjunction with norm to normalize luminance data. If either is None, it is autoscaled to the respective min or max of the color array C. If not None, vmin or vmax passed in here override any pre-existing values supplied in the norm instance.

edgecolors : {None, ‘none’, color, color sequence}

If None, the rc setting is used by default. If ‘none’, edges will not be visible. An mpl color or sequence of colors will set the edge color.

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.

Returns:

collection : matplotlib.collections.Collection

Other Parameters:

antialiaseds : bool, optional, 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"], which defaults to True. Stroking the edges may be preferred if alpha is 1, but will cause artifacts otherwise.

**kwargs :

Any unused keyword arguments 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	float or None
animated	bool
antialiased or antialiaseds	Boolean or sequence of booleans
array	ndarray
capstyle	unknown
clim	a length 2 sequence of floats; may be overridden in methods that have vmin and vmax kwargs.
clip_box	a Bbox instance
clip_on	bool
clip_path	[(Path, Transform) | Patch | None]
cmap	a colormap or registered colormap name
color	matplotlib color arg or sequence of rgba tuples
contains	a callable function
edgecolor or edgecolors	matplotlib color spec or sequence of specs
facecolor or facecolors	matplotlib color spec or sequence of specs
figure	a Figure instance
gid	an id string
hatch	[ ‘/’ | ‘' | ‘|’ | ‘-‘ | ‘+’ | ‘x’ | ‘o’ | ‘O’ | ‘.’ | ‘*’ ]
joinstyle	unknown
label	object
linestyle or dashes or linestyles	[‘solid’ | ‘dashed’, ‘dashdot’, ‘dotted’ | (offset, on-off-dash-seq) | '-' | '--' | '-.' | ':' | 'None' | ' ' | '']
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 | bool | float | callable]
pickradius	float distance in points
rasterized	bool or None
sketch_params	(scale: float, length: float, randomness: float)
snap	bool or None
transform	Transform
url	a url string
urls	List[str] or None
visible	bool
zorder	float

See also

pcolormesh

for an explanation of the differences between pcolor and pcolormesh.

Notes

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.

The grid orientation follows the MATLAB convention: an array C with shape (nrows, ncolumns) is plotted with the column number as X and the row number as Y, increasing up; hence it is plotted the way the array would be printed, except that the Y axis is reversed. That is, C is taken as C (y, x).

Similarly for meshgrid():

x = np.arange(5)
y = np.arange(3)
X, Y = np.meshgrid(x, y)

is equivalent to:

X = array([[0, 1, 2, 3, 4],
           [0, 1, 2, 3, 4],
           [0, 1, 2, 3, 4]])

Y = array([[0, 0, 0, 0, 0],
           [1, 1, 1, 1, 1],
           [2, 2, 2, 2, 2]])

so if you have:

C = rand(len(x), len(y))

then you need to transpose C:

pcolor(X, Y, C.T)

or:

pcolor(C.T)

MATLAB pcolor() always discards the last row and column of C, but Matplotlib displays the last row and column if X and Y are not specified, or if X and Y have one more row and column than C.

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.