Merge pull request matplotlib#2591 from dopplershift/fix-infinite-recursion

Fix infinite recursion in units with ndarray subclasses.

Author: mdboom

lib/matplotlib/units.py

@@ -145,7 +145,13 @@ def get_converter(self, x):
                     return converter
             except AttributeError:
                 # not a masked_array
-                converter = self.get_converter(xravel[0])
+                # Make sure we don't recurse forever -- it's possible for
+                # ndarray subclasses to continue to return subclasses and
+                # not ever return a non-subclass for a single element.
+                next_item = xravel[0]
+                if (not isinstance(next_item, np.ndarray) or
+                    next_item.shape != x.shape):
+                    converter = self.get_converter(next_item)
                 return converter
 
         if converter is None and iterable(x):