@@ -1739,14 +1739,42 @@ def _initialize_x_y(self, z):
17391739 are not given explicitly via *levels*.
17401740 Defaults to `~.ticker.MaxNLocator`.
17411741
1742- extend : {'neither', 'both', 'min', 'max'}, optional
1743- Unless this is 'neither', contour levels are automatically
1744- added to one or both ends of the range so that all data
1745- are included. These added ranges are then mapped to the
1746- special colormap values which default to the ends of the
1747- colormap range, but can be set via
1748- :meth:`matplotlib.colors.Colormap.set_under` and
1749- :meth:`matplotlib.colors.Colormap.set_over` methods.
1742+ extend : {'neither', 'both', 'min', 'max'}, optional, default: \
1743+
1744+ Determines the ``contourf``-coloring of values that are outside the
1745+ *levels* range.
1746+
1747+ If 'neither', values outside the *levels* range are not colored.
1748+ If 'min', 'max' or 'both', color the values below, above or below
1749+ and above the *levels* range.
1750+
1751+ Values below ``min(levels)`` and above ``max(levels)`` are mapped
1752+ to the under/over values of the `.Colormap`. Note, that most
1753+ colormaps do not have dedicated colors for these by default, so
1754+ that the over and under values are the edge values of the colormap.
1755+ You may want to set these values explicitly using
1756+ `.Colormap.set_under` and `.Colormap.set_over`.
1757+
1758+ .. note::
1759+
1760+ An exising `.QuadContourSet` does not get notified if
1761+ properties of its colormap are changed. Therefore, an explicit
1762+ call `.QuadContourSet.changed()` is needed after modifying the
1763+ colormap. The explicit call can be left out, if a colorbar is
1764+ assigned to the `.QuadContourSet` because it interally calls
1765+ `.QuadContourSet.changed()`.
1766+
1767+ Example::
1768+
1769+ x = np.arange(1, 10)
1770+ y = x.reshape(-1, 1)
1771+ h = x * y
1772+
1773+ cs = plt.contourf(h, levels=[10, 30, 50],
1774+ colors=['#808080', '#A0A0A0', '#C0C0C0'], extend='both')
1775+ cs.cmap.set_over('red')
1776+ cs.cmap.set_under('blue')
1777+ cs.changed()
17501778
17511779 xunits, yunits : registered units, optional
17521780 Override axis units by specifying an instance of a
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