@@ -1775,14 +1775,42 @@ def _initialize_x_y(self, z):
17751775 are not given explicitly via *levels*.
17761776 Defaults to `~.ticker.MaxNLocator`.
17771777
1778- extend : {'neither', 'both', 'min', 'max'}, optional
1779- Unless this is 'neither', contour levels are automatically
1780- added to one or both ends of the range so that all data
1781- are included. These added ranges are then mapped to the
1782- special colormap values which default to the ends of the
1783- colormap range, but can be set via
1784- :meth:`matplotlib.colors.Colormap.set_under` and
1785- :meth:`matplotlib.colors.Colormap.set_over` methods.
1778+ extend : {'neither', 'both', 'min', 'max'}, optional, default: \
1779+
1780+ Determines the ``contourf``-coloring of values that are outside the
1781+ *levels* range.
1782+
1783+ If 'neither', values outside the *levels* range are not colored.
1784+ If 'min', 'max' or 'both', color the values below, above or below
1785+ and above the *levels* range.
1786+
1787+ Values below ``min(levels)`` and above ``max(levels)`` are mapped
1788+ to the under/over values of the `.Colormap`. Note, that most
1789+ colormaps do not have dedicated colors for these by default, so
1790+ that the over and under values are the edge values of the colormap.
1791+ You may want to set these values explicitly using
1792+ `.Colormap.set_under` and `.Colormap.set_over`.
1793+
1794+ .. note::
1795+
1796+ An exising `.QuadContourSet` does not get notified if
1797+ properties of its colormap are changed. Therefore, an explicit
1798+ call `.QuadContourSet.changed()` is needed after modifying the
1799+ colormap. The explicit call can be left out, if a colorbar is
1800+ assigned to the `.QuadContourSet` because it interally calls
1801+ `.QuadContourSet.changed()`.
1802+
1803+ Example::
1804+
1805+ x = np.arange(1, 10)
1806+ y = x.reshape(-1, 1)
1807+ h = x * y
1808+
1809+ cs = plt.contourf(h, levels=[10, 30, 50],
1810+ colors=['#808080', '#A0A0A0', '#C0C0C0'], extend='both')
1811+ cs.cmap.set_over('red')
1812+ cs.cmap.set_under('blue')
1813+ cs.changed()
17861814
17871815 xunits, yunits : registered units, optional
17881816 Override axis units by specifying an instance of a
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