Prevent Inf from screwing colorbar scale. (#2120)

pd.isnull([np.inf]) is True while np.isfinite([np.inf]) is False.
Let's use the latter.

Author: dcherian

doc/whats-new.rst

@@ -65,6 +65,8 @@ Bug fixes
   By `Deepak Cherian <https://github.com/dcherian>`_.
 - ``plot.line()`` learned new kwargs: ``xincrease``, ``yincrease`` that change the direction of the respective axes.
   By `Deepak Cherian <https://github.com/dcherian>`_.
+- Colorbar limits are now determined by excluding ±Infs too.
+  By `Deepak Cherian <https://github.com/dcherian>`_.
 
 .. _whats-new.0.10.3:
 

xarray/plot/utils.py

@@ -160,7 +160,7 @@ def _determine_cmap_params(plot_data, vmin=None, vmax=None, cmap=None,
     """
     import matplotlib as mpl
 
-    calc_data = np.ravel(plot_data[~pd.isnull(plot_data)])
+    calc_data = np.ravel(plot_data[np.isfinite(plot_data)])
 
     # Handle all-NaN input data gracefully
     if calc_data.size == 0:

xarray/tests/test_plot.py

@@ -426,6 +426,15 @@ def test_center(self):
         assert cmap_params['levels'] is None
         assert cmap_params['norm'] is None
 
+    def test_nan_inf_are_ignored(self):
+        cmap_params1 = _determine_cmap_params(self.data)
+        data = self.data
+        data[50:55] = np.nan
+        data[56:60] = np.inf
+        cmap_params2 = _determine_cmap_params(data)
+        assert cmap_params1['vmin'] == cmap_params2['vmin']
+        assert cmap_params1['vmax'] == cmap_params2['vmax']
+
     @pytest.mark.slow
     def test_integer_levels(self):
         data = self.data + 1