>>> """
=============
Contourf Demo
=============

How to use the `.axes.Axes.contourf` method to create filled contour plots.
"""
... import numpy as np
... import matplotlib.pyplot as plt
... 
... origin = 'lower'
... 
... delta = 0.025
... 
... x = y = np.arange(-3.0, 3.01, delta)
... X, Y = np.meshgrid(x, y)
... Z1 = np.exp(-X**2 - Y**2)
... Z2 = np.exp(-(X - 1)**2 - (Y - 1)**2)
... Z = (Z1 - Z2) * 2
... 
... nr, nc = Z.shape
... 
... # put NaNs in one corner:
... Z[-nr // 6:, -nc // 6:] = np.nan
... # contourf will convert these to masked
... 
... 
... Z = np.ma.array(Z)
... # mask another corner:
... Z[:nr // 6, :nc // 6] = np.ma.masked
... 
... # mask a circle in the middle:
... interior = np.sqrt(X**2 + Y**2) < 0.5
... Z[interior] = np.ma.masked
... 
... #############################################################################
... # Automatic contour levels
... # ------------------------
... # We are using automatic selection of contour levels; this is usually not such
... # a good idea, because they don't occur on nice boundaries, but we do it here
... # for purposes of illustration.
... 
... fig1, ax2 = plt.subplots(constrained_layout=True)
... CS = ax2.contourf(X, Y, Z, 10, cmap=plt.cm.bone, origin=origin)
... 
... # Note that in the following, we explicitly pass in a subset of the contour
... # levels used for the filled contours.  Alternatively, we could pass in
... # additional levels to provide extra resolution, or leave out the *levels*
... # keyword argument to use all of the original levels.
... 
... CS2 = ax2.contour(CS, levels=CS.levels[::2], colors='r', origin=origin)
... 
... ax2.set_title('Nonsense (3 masked regions)')
... ax2.set_xlabel('word length anomaly')
... ax2.set_ylabel('sentence length anomaly')
... 
... # Make a colorbar for the ContourSet returned by the contourf call.
... cbar = fig1.colorbar(CS)
... cbar.ax.set_ylabel('verbosity coefficient')
... # Add the contour line levels to the colorbar
... cbar.add_lines(CS2)
... 
... #############################################################################
... # Explicit contour levels
... # -----------------------
... # Now make a contour plot with the levels specified, and with the colormap
... # generated automatically from a list of colors.
... 
... fig2, ax2 = plt.subplots(constrained_layout=True)
... levels = [-1.5, -1, -0.5, 0, 0.5, 1]
... CS3 = ax2.contourf(X, Y, Z, levels,
...                    colors=('r', 'g', 'b'),
...                    origin=origin,
...                    extend='both')
... # Our data range extends outside the range of levels; make
... # data below the lowest contour level yellow, and above the
... # highest level cyan:
... CS3.cmap.set_under('yellow')
... CS3.cmap.set_over('cyan')
... 
... CS4 = ax2.contour(X, Y, Z, levels,
...                   colors=('k',),
...                   linewidths=(3,),
...                   origin=origin)
... ax2.set_title('Listed colors (3 masked regions)')
... ax2.clabel(CS4, fmt='%2.1f', colors='w', fontsize=14)
... 
... # Notice that the colorbar gets all the information it
... # needs from the ContourSet object, CS3.
... fig2.colorbar(CS3)
... 
... #############################################################################
... # Extension settings
... # ------------------
... # Illustrate all 4 possible "extend" settings:
... extends = ["neither", "both", "min", "max"]
... cmap = plt.colormaps["winter"].with_extremes(under="magenta", over="yellow")
... # Note: contouring simply excludes masked or nan regions, so
... # instead of using the "bad" colormap value for them, it draws
... # nothing at all in them.  Therefore the following would have
... # no effect:
... # cmap.set_bad("red")
... 
... fig, axs = plt.subplots(2, 2, constrained_layout=True)
... 
... for ax, extend in zip(axs.flat, extends):
...     cs = ax.contourf(X, Y, Z, levels, cmap=cmap, extend=extend, origin=origin)
...     fig.colorbar(cs, ax=ax, shrink=0.9)
...     ax.set_title("extend = %s" % extend)
...     ax.locator_params(nbins=4)
... 
... plt.show()
... 
... #############################################################################
... #
... # .. admonition:: References
... #
... #    The use of the following functions, methods, classes and modules is shown
... #    in this example:
... #
... #    - `matplotlib.axes.Axes.contour` / `matplotlib.pyplot.contour`
... #    - `matplotlib.axes.Axes.contourf` / `matplotlib.pyplot.contourf`
... #    - `matplotlib.axes.Axes.clabel` / `matplotlib.pyplot.clabel`
... #    - `matplotlib.figure.Figure.colorbar` / `matplotlib.pyplot.colorbar`
... #    - `matplotlib.colors.Colormap`
... #    - `matplotlib.colors.Colormap.set_bad`
... #    - `matplotlib.colors.Colormap.set_under`
... #    - `matplotlib.colors.Colormap.set_over`
...