handle NaN case nicely in _is_sorted

perimosocordiae · perimosocordiae · commit e3796c27e6e9 · 2014-01-19T03:47:18.000-05:00
Previously, the `&gt;=` comparison would cause a
"RuntimeWarning: invalid value encountered in greater_equal".

Here, `np.amin` propagates NaN values appropriately
and doesn't cause the warning to throw.
diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
@@ -504,7 +504,7 @@ def _is_sorted(self, x):
         """return true if x is sorted"""
         if len(x) < 2:
             return 1
-        return np.alltrue(x[1:] - x[0:-1] >= 0)
+        return np.amin(x[1:] - x[0:-1]) >= 0
 
     @allow_rasterization
     def draw(self, renderer):
