Add the __add__ method, and doc.

lkilcher · lkilcher · commit f06bf467ccc2 · 2018-05-17T16:33:38.000-06:00
diff --git a/lib/matplotlib/colors.py b/lib/matplotlib/colors.py
@@ -650,6 +650,11 @@ def join(self, other, name=None, frac_self=None, N=None):
         # Note that `joined_cmap` will be 2/3 `cmap1`, and 1/3 `cmap2`
         # because of the default behavior of frac_self
         # (i.e. proportional to N of each cmap).
+
+        # This is also available as :meth:`Colormap.__add__`, so that
+        # the following is possible:
+
+        joined_cmap = cmap1 + cmap2
         """
         if N is None:
             N = self.N + other.N
@@ -664,6 +669,8 @@ def join(self, other, name=None, frac_self=None, N=None):
         # N is set by len of the vstack'd array:
         return ListedColormap(np.vstack((map0, map1)), name, )
 
+    __add__ = join
+
     def truncate(self, minval=0.0, maxval=1.0, N=None):
         """
         Truncate a colormap.
