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 topcolor
. It's much faster and preferred in most cases. For a detailed discussion on the differences see Differences between pcolor() and pcolormesh().Parameters: - Carray-like
A scalar 2-D array. The values will be color-mapped.
- X, Yarray-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.
- cmapstr or
Colormap
, optional A Colormap instance or registered colormap name. The colormap maps the C values to colors. Defaults to
rcParams["image.cmap"]
(default: 'viridis').- 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, vmaxscalar, 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"]
(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 form edgecolor works as an alias.
- alphascalar, 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.
- '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
- snapbool, optional, default: False
Whether to snap the mesh to pixel boundaries.
Returns: 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 antialiasedsbool or sequence of bools array
ndarray capstyle
{'butt', 'round', 'projecting'} clim
(vmin: float, vmax: float) clip_box
Bbox
clip_on
bool clip_path
Patch or (Path, Transform) or None cmap
colormap or registered colormap name color
color or sequence of rgba tuples contains
callable edgecolor
or ec or edgecolorscolor or sequence of colors or 'face' facecolor
or facecolors or fccolor 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 lwfloat or sequence of floats norm
Normalize
offset_position
{'screen', 'data'} offsets
array-like (N, 2) or (2,) 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. Usepcolor
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 aPolyCollection
,pcolormesh
returns aQuadMesh
. 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
andpcolormesh
support masked arrays for C. However, onlypcolor
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 inpcolor
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 withpcolor
.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
).