pcolormesh(*args, alpha=None, norm=None, cmap=None, vmin=None, vmax=None, shading=None, antialiased=False, data=None, **kwargs)
Call signature:
pcolormesh([X, Y,] C, **kwargs)
X and Y can be used to specify the corners of the quadrilaterals.
.. hint::
`~.Axes.pcolormesh` is similar to `~.Axes.pcolor`. It is much faster
and preferred in most cases. For a detailed discussion on the
differences see :ref:`Differences between pcolor() and pcolormesh()
<differences-pcolor-pcolormesh>`.
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. Use ~.Axes.pcolor
if you need this functionality.
<Unimplemented 'target' '.. _axes-pcolormesh-grid-orientation:'>
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.
<Unimplemented 'target' '.. _differences-pcolor-pcolormesh:'>
Differences between pcolor() and pcolormesh()
Both methods are used to create a pseudocolor plot of a 2D array using quadrilaterals.
The main difference lies in the created object and internal data handling: While ~.Axes.pcolor
returns a .PolyCollection
, ~.Axes.pcolormesh
returns a .QuadMesh
. 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 ~.Axes.pcolor
and ~.Axes.pcolormesh
support masked arrays for C. However, only ~.Axes.pcolor
supports masked arrays for X and Y. The reason lies in the internal handling of the masked values. ~.Axes.pcolor
leaves out the respective polygons from the PolyCollection. ~.Axes.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 in ~.Axes.pcolor
is not drawn as the corresponding polygons do not exist in the PolyCollection.
Another difference is the support of Gouraud shading in ~.Axes.pcolormesh
, which is not available with ~.Axes.pcolor
.
If given, all parameters also accept a string s
, which is interpreted as data[s]
(unless this raises an exception).
Additionally, the following arguments are allowed. They are passed along to the ~matplotlib.collections.QuadMesh
constructor:
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: (M, N) array-like or M*N array-like 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
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
The color-mapped values.
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 <axes-pcolormesh-grid-orientation>
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'
or 'gouraud'
, the dimensions of X and Y should be the same as those of C (if not, a ValueError will be raised). For 'nearest'
the color C[i, j]
is centered on (X[i, j], Y[i, j])
. For 'gouraud'
, a smooth interpolation is caried out between the quadrilateral corners.
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.
A Colormap instance or registered colormap name. The colormap maps the C values to colors.
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.
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.
The color of the edges. Defaults to 'none'. Possible values:
'none' or '': No edge.
None: patch.edgecolor
will be used. Note that currently patch.force_edgecolor
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.
The alpha blending value, between 0 (transparent) and 1 (opaque).
The fill style for the quadrilateral; defaults to 'flat' or pcolor.shading
. 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.
'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. The dimensions of X and Y must be the same as C. When Gouraud shading is used, edgecolors is ignored.
'auto': Choose 'flat' if dimensions of X and Y are one larger than C. Choose 'nearest' if dimensions are the same.
See /gallery/images_contours_and_fields/pcolormesh_grids
for more description.
Whether to snap the mesh to pixel boundaries.
Rasterize the pcolormesh when drawing vector graphics. This can speed up rendering and produce smaller files for large data sets. See also /gallery/misc/rasterization_demo
.
Create a pseudocolor plot with a non-regular rectangular grid.
imshow
If X and Y are each equidistant, :None:None:`~.Axes.imshow` can be a faster alternative.
pcolor
An alternative implementation with slightly different features. For a detailed discussion on the differences see :None:ref:`Differences between pcolor() and pcolormesh()
<differences-pcolor-pcolormesh>`.
The following pages refer to to this document either explicitly or contain code examples using this.
scipy.signal._waveforms.chirp
scipy.interpolate._ndgriddata.NearestNDInterpolator
scipy.signal._spectral_py.stft
scipy.signal._wavelets.morlet2
scipy.signal._spectral_py.spectrogram
scipy.interpolate.interpnd.LinearNDInterpolator
scipy.signal._spectral_py.istft
matplotlib.pyplot.pcolor
matplotlib.pyplot.plotting
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