matplotlib.pyplot.pcolormesh #

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

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

Call signature:

pcolormesh([X,Y,]C,/,**kwargs)

X andY can be used to specify the corners of the quadrilaterals.

The argumentsX,Y,C are positional-only.

Hint

pcolormesh is similar topcolor. It is much fasterand preferred in most cases. For a detailed discussion on thedifferences seeDifferences between pcolor() and pcolormesh().

Parameters:

Carray-like

The mesh data. Supported array shapes are:

(M, N) or M*N: a mesh with scalar data. The values are mapped tocolors using normalization and a colormap. See parametersnorm,cmap,vmin,vmax.
(M, N, 3): an image with RGB values (0-1 float or 0-255 int).
(M, N, 4): an image with RGBA values (0-1 float or 0-255 int),i.e. including transparency.

The first two dimensions (M, N) define the rows and columns ofthe mesh data.

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, andthe row index corresponds to y. For details, see theNotes section below.

Ifshading='flat' the dimensions ofX andY should be onegreater than those ofC, and the quadrilateral is colored dueto the value atC[i,j]. IfX,Y andC have equaldimensions, a warning will be raised and the last row and columnofC will be ignored.

Ifshading='nearest' or'gouraud', the dimensions ofXandY should be the same as those ofC (if not, a ValueErrorwill be raised). For'nearest' the colorC[i,j] iscentered on(X[i,j],Y[i,j]). For'gouraud', a smoothinterpolation is carried out between the quadrilateral corners.

IfX and/orY are 1-D arrays or column vectors they will beexpanded as needed into the appropriate 2D arrays, making arectangular grid.

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

The Colormap instance or registered colormap name used to map scalar datato colors.

normstr orNormalize, optional

The normalization method used to scale scalar data to the [0, 1] rangebefore mapping to colors usingcmap. By default, a linear scaling isused, mapping the lowest value to 0 and the highest to 1.

If given, this can be one of the following:

An instance ofNormalize or one of its subclasses(seeColormap normalization).
A scale name, i.e. one of "linear", "log", "symlog", "logit", etc. For alist of available scales, callmatplotlib.scale.get_scale_names().In that case, a suitableNormalize subclass is dynamically generatedand instantiated.

vmin, vmaxfloat, optional

When using scalar data and no explicitnorm,vmin andvmax definethe data range that the colormap covers. By default, the colormap coversthe complete value range of the supplied data. It is an error to usevmin/vmax when anorm instance is given (but using astrnormname together withvmin/vmax is acceptable).

colorizerColorizer or None, default: None

The Colorizer object used to map color to data. If None, a Colorizerobject is created from anorm andcmap.

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 currentlyrcParams["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 formedgecolor works as an alias.

alphafloat, default: None

The alpha blending value, between 0 (transparent) and 1 (opaque).

shading{'flat', 'nearest', 'gouraud', 'auto'}, optional

The fill style for the quadrilateral; defaults torcParams["pcolor.shading"] (default:'auto'). Possible values:

'flat': A solid color is used for each quad. The color of thequad (i, j), (i+1, j), (i, j+1), (i+1, j+1) is given byC[i,j]. The dimensions ofX andY should beone greater than those ofC; if they are the same asC,then a deprecation warning is raised, and the last rowand column ofC are dropped.
'nearest': Each grid point will have a color centered on it,extending halfway between the adjacent grid centers. Thedimensions ofX andY must be the same asC.
'gouraud': Each quad will be Gouraud shaded: The color of thecorners (i', j') are given byC[i',j']. The color values ofthe area in between is interpolated from the corner values.The dimensions ofX andY must be the same asC. WhenGouraud shading is used,edgecolors is ignored.
'auto': Choose 'flat' if dimensions ofX andY are onelarger thanC. Choose 'nearest' if dimensions are the same.

Seepcolormesh grids and shadingfor more description.

snapbool, default: False

Whether to snap the mesh to pixel boundaries.

rasterizedbool, optional

Rasterize the pcolormesh when drawing vector graphics. This canspeed up rendering and produce smaller files for large data sets.See alsoRasterization for vector graphics.

Returns:

matplotlib.collections.QuadMesh

Other Parameters:

dataindexable object, optional

If given, all parameters also accept a strings, which isinterpreted asdata[s] ifs is a key indata.

**kwargs

Additionally, the following arguments are allowed. They are passedalong to theQuadMesh 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 and two offsets from the bottom left corner of the image
`alpha`	array-like or float or None
`animated`	bool
`antialiased` or`aa` or`antialiaseds`	bool or list of bools
`array`	array-like
`capstyle`	`CapStyle` or {'butt', 'projecting', 'round'}
`clim`	(vmin: float, vmax: float)
`clip_box`	`BboxBase` or None
`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 ofcolor or 'face'
`facecolor` or`facecolors` or`fc`	color or list ofcolor
`figure`	`Figure` or`SubFigure`
`gid`	str
`hatch`	{'/', '\', '\|', '-', '+', 'x', 'o', 'O', '.', '*'}
`hatch_linewidth`	unknown
`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
`mouseover`	bool
`norm`	`Normalize` or str or None
`offset_transform` or`transOffset`	`Transform`
`offsets`	(N, 2) or (2,) array-like
`path_effects`	list of`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

pcolor: An alternative implementation with slightly different features. For a detailed discussion on the differences seeDifferences between pcolor() and pcolormesh().
imshow: IfX andY are each equidistant,imshow can be a faster alternative.

Notes

Note

This is thepyplot wrapper foraxes.Axes.pcolormesh.

Masked arrays

C may be a masked array. IfC[i,j] is masked, the correspondingquadrilateral will be transparent. Masking ofX andY is notsupported. Usepcolor if you need this functionality.

Grid orientation

The grid orientation follows the standard matrix convention: An arrayC with shape (nrows, ncolumns) is plotted with the column number asX and the row number asY.

Differences between pcolor() and pcolormesh()

Both methods are used to create a pseudocolor plot of a 2D arrayusing quadrilaterals.

The main difference lies in the created object and internal datahandling:Whilepcolor returns aPolyQuadMesh,pcolormeshreturns aQuadMesh. The latter is more specialized for the givenpurpose and thus is faster. It should almost always be preferred.

There is also a slight difference in the handling of masked arrays.Bothpcolor andpcolormesh support masked arraysforC. However, onlypcolor supports masked arrays forXandY. The reason lies in the internal handling of the masked values.pcolor leaves out the respective polygons from thePolyQuadMesh.pcolormesh sets the facecolor of the maskedelements to transparent. You can see the difference when usingedgecolors. While all edges are drawn irrespective of masking in aQuadMesh, the edge between two adjacent masked quadrilaterals inpcolor is not drawn as the corresponding polygons do notexist in the PolyQuadMesh. Because PolyQuadMesh draws each individualpolygon, it also supports applying hatches and linestyles to the collection.