matplotlib.axes.Axes.contourf

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

Plot filled contours.

Call signature:

contourf([X, Y,] Z, [levels], **kwargs)

contour and contourf draw contour lines and filled contours, respectively. Except as noted, function signatures and return values are the same for both versions.

Parameters:

X, Yarray-like, optional

The coordinates of the values in Z.

X and Y must both be 2D with the same shape as Z (e.g. created via numpy.meshgrid), or they must both be 1-D such that len(X) == N is the number of columns in Z and len(Y) == M is the number of rows in Z.

X and Y must both be ordered monotonically.

If not given, they are assumed to be integer indices, i.e. X = range(N), Y = range(M).

Z(M, N) array-like

The height values over which the contour is drawn. Color-mapping is controlled by cmap, norm, vmin, and vmax.

levelsint or array-like, optional

Determines the number and positions of the contour lines / regions.

If an int n, use MaxNLocator, which tries to automatically choose no more than n+1 "nice" contour levels between vmin and vmax.

If array-like, draw contour lines at the specified levels. The values must be in increasing order.

Returns:

QuadContourSet

Other Parameters:

corner_maskbool, default: rcParams["contour.corner_mask"] (default: True)

Enable/disable corner masking, which only has an effect if Z is a masked array. If False, any quad touching a masked point is masked out. If True, only the triangular corners of quads nearest those points are always masked out, other triangular corners comprising three unmasked points are contoured as usual.

colorscolor string or sequence of colors, optional

The colors of the levels, i.e. the lines for contour and the areas for contourf.

The sequence is cycled for the levels in ascending order. If the sequence is shorter than the number of levels, it's repeated.

As a shortcut, single color strings may be used in place of one-element lists, i.e. 'red' instead of ['red'] to color all levels with the same color. This shortcut does only work for color strings, not for other ways of specifying colors.

By default (value None), the colormap specified by cmap will be used.

alphafloat, default: 1

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

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

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

This parameter is ignored if colors is set.

normstr or Normalize, optional

The normalization method used to scale scalar data to the [0, 1] range before mapping to colors using cmap. By default, a linear scaling is used, mapping the lowest value to 0 and the highest to 1.

If given, this can be one of the following:

• An instance of Normalize or one of its subclasses (see Colormap Normalization).

• A scale name, i.e. one of "linear", "log", "symlog", "logit", etc. For a list of available scales, call matplotlib.scale.get_scale_names(). In that case, a suitable Normalize subclass is dynamically generated and instantiated.

This parameter is ignored if colors is set.

vmin, vmaxfloat, optional

When using scalar data and no explicit norm, vmin and vmax define the data range that the colormap covers. By default, the colormap covers the complete value range of the supplied data. It is an error to use vmin/vmax when a norm instance is given (but using a str norm name together with vmin/vmax is acceptable).

If vmin or vmax are not given, the default color scaling is based on levels.

This parameter is ignored if colors is set.

origin{None, 'upper', 'lower', 'image'}, default: None

Determines the orientation and exact position of Z by specifying the position of Z[0, 0]. This is only relevant, if X, Y are not given.

• None: Z[0, 0] is at X=0, Y=0 in the lower left corner.

• 'lower': Z[0, 0] is at X=0.5, Y=0.5 in the lower left corner.

• 'upper': Z[0, 0] is at X=N+0.5, Y=0.5 in the upper left corner.

• 'image': Use the value from rcParams["image.origin"] (default: 'upper').

extent(x0, x1, y0, y1), optional

If origin is not None, then extent is interpreted as in imshow: it gives the outer pixel boundaries. In this case, the position of Z[0, 0] is the center of the pixel, not a corner. If origin is None, then (x0, y0) is the position of Z[0, 0], and (x1, y1) is the position of Z[-1, -1].

This argument is ignored if X and Y are specified in the call to contour.

locatorticker.Locator subclass, optional

The locator is used to determine the contour levels if they are not given explicitly via levels. Defaults to MaxNLocator.

extend{'neither', 'both', 'min', 'max'}, default: 'neither'

Determines the contourf-coloring of values that are outside the levels range.

If 'neither', values outside the levels range are not colored. If 'min', 'max' or 'both', color the values below, above or below and above the levels range.

Values below min(levels) and above max(levels) are mapped to the under/over values of the Colormap. Note that most colormaps do not have dedicated colors for these by default, so that the over and under values are the edge values of the colormap. You may want to set these values explicitly using Colormap.set_under and Colormap.set_over.

Note

An existing QuadContourSet does not get notified if properties of its colormap are changed. Therefore, an explicit call QuadContourSet.changed() is needed after modifying the colormap. The explicit call can be left out, if a colorbar is assigned to the QuadContourSet because it internally calls QuadContourSet.changed().

Example:

x = np.arange(1, 10)
y = x.reshape(-1, 1)
h = x * y

cs = plt.contourf(h, levels=[10, 30, 50],
    colors=['#808080', '#A0A0A0', '#C0C0C0'], extend='both')
cs.cmap.set_over('red')
cs.cmap.set_under('blue')
cs.changed()

xunits, yunitsregistered units, optional

Override axis units by specifying an instance of a matplotlib.units.ConversionInterface.

antialiasedbool, optional

Enable antialiasing, overriding the defaults. For filled contours, the default is True. For line contours, it is taken from rcParams["lines.antialiased"] (default: True).

nchunkint >= 0, optional

If 0, no subdivision of the domain. Specify a positive integer to divide the domain into subdomains of nchunk by nchunk quads. Chunking reduces the maximum length of polygons generated by the contouring algorithm which reduces the rendering workload passed on to the backend and also requires slightly less RAM. It can however introduce rendering artifacts at chunk boundaries depending on the backend, the antialiased flag and value of alpha.

linewidthsfloat or array-like, default: rcParams["contour.linewidth"] (default: None)

Only applies to contour.

The line width of the contour lines.

If a number, all levels will be plotted with this linewidth.

If a sequence, the levels in ascending order will be plotted with the linewidths in the order specified.

If None, this falls back to rcParams["lines.linewidth"] (default: 1.5).

linestyles{None, 'solid', 'dashed', 'dashdot', 'dotted'}, optional

Only applies to contour.

If linestyles is None, the default is 'solid' unless the lines are monochrome. In that case, negative contours will instead take their linestyle from the negative_linestyles argument.

linestyles can also be an iterable of the above strings specifying a set of linestyles to be used. If this iterable is shorter than the number of contour levels it will be repeated as necessary.

negative_linestyles{None, 'solid', 'dashed', 'dashdot', 'dotted'}, optional

Only applies to contour.

If linestyles is None and the lines are monochrome, this argument specifies the line style for negative contours.

If negative_linestyles is None, the default is taken from rcParams["contour.negative_linestyles"].

negative_linestyles can also be an iterable of the above strings specifying a set of linestyles to be used. If this iterable is shorter than the number of contour levels it will be repeated as necessary.

hatcheslist[str], optional

Only applies to contourf.

A list of cross hatch patterns to use on the filled areas. If None, no hatching will be added to the contour. Hatching is supported in the PostScript, PDF, SVG and Agg backends only.

algorithm{'mpl2005', 'mpl2014', 'serial', 'threaded'}, optional

Which contouring algorithm to use to calculate the contour lines and polygons. The algorithms are implemented in ContourPy, consult the ContourPy documentation for further information.

The default is taken from rcParams["contour.algorithm"] (default: 'mpl2014').

dataindexable object, optional

If given, all parameters also accept a string s, which is interpreted as data[s] (unless this raises an exception).

Notes

1. contourf differs from the MATLAB version in that it does not draw the polygon edges. To draw edges, add line contours with calls to contour.

2. contourf fills intervals that are closed at the top; that is, for boundaries z1 and z2, the filled region is:

   z1 < Z <= z2
   

   except for the lowest interval, which is closed on both sides (i.e. it includes the lowest value).

3. contour and contourf use a marching squares algorithm to compute contour locations. More information can be found in ContourPy documentation.

Examples using matplotlib.axes.Axes.contourf

Contour Corner Mask

Contour Corner Mask

Contourf Demo

Contourf Demo

Contourf Hatching

Contourf Hatching

Contourf and log color scale

Contourf and log color scale

Contour plot of irregularly spaced data

Contour plot of irregularly spaced data

pcolormesh

pcolormesh

3D box surface plot

3D box surface plot

Filled contours

Filled contours

Projecting filled contour onto a graph

Projecting filled contour onto a graph

contourf(X, Y, Z)

contourf(X, Y, Z)