BUG: Ignore NaN in setting mn and mx (#877) (#878)

* ignore nan in setting mn and mx

* test if vmin vmax set correctly for array with NaN

* test compatible with older versions

* reference to issue and shorter assert in test

geopandas/plotting.py

@@ -453,8 +453,8 @@ def plot_dataframe(df, column=None, cmap=None, color=None, ax=None,
                       for i in range(len(binedges)-1)]
         values = np.array(binning.yb)
 
-    mn = values.min() if vmin is None else vmin
-    mx = values.max() if vmax is None else vmax
+    mn = values[~np.isnan(values)].min() if vmin is None else vmin
+    mx = values[~np.isnan(values)].max() if vmax is None else vmax
 
     geom_types = df.geometry.type
     poly_idx = np.asarray((geom_types == 'Polygon')

geopandas/tests/test_plotting.py

@@ -261,6 +261,10 @@ def setup_method(self):
         self.df2 = GeoDataFrame({'geometry': [multipoly1, multipoly2],
                                  'values': [0, 1]})
 
+        t3 = Polygon([(2, 0), (3, 0), (3, 1)])
+        df_nan = GeoDataFrame({'geometry': t3, 'values': [np.nan]})
+        self.df3 = self.df.append(df_nan)
+
     def test_single_color(self):
 
         ax = self.polys.plot(color='green')
@@ -290,6 +294,12 @@ def test_vmin_vmax(self):
         actual_colors = ax.collections[0].get_facecolors()
         np.testing.assert_array_equal(actual_colors[0], actual_colors[1])
 
+        # vmin vmax set correctly for array with NaN (GitHub issue 877)
+        ax = self.df3.plot(column='values')
+        actual_colors = ax.collections[0].get_facecolors()
+        assert np.any(np.not_equal(actual_colors[0], actual_colors[1]))
+
+
     def test_style_kwargs(self):
 
         # facecolor overrides default cmap when color is not set