BUG/VIS: fix Series.hist so that users can create hist subplots without the mpl API

Author: cpcloud

doc/source/release.rst

@@ -98,6 +98,8 @@ pandas 0.13
     with the usecols parameter (:issue: `3192`)
   - Fix an issue in merging blocks where the resulting DataFrame had partially
     set _ref_locs (:issue:`4403`)
+  - Fixed an issue where hist subplots were being overwritten when they were
+    called using the top level matplotlib API (:issue:`4408`)
 
 pandas 0.12
 ===========

pandas/tests/test_graphics.py

@@ -662,11 +662,24 @@ def test_hist_layout(self):
         # invalid format for layout
         self.assertRaises(ValueError, df.hist, layout=(1,))
 
+    @slow
+    def test_hist_no_overlap(self):
+        from matplotlib.pyplot import subplot, close, gcf
+        x = Series(np.random.randn(2))
+        y = Series(np.random.randn(2))
+        subplot(121)
+        x.hist()
+        subplot(122)
+        y.hist()
+        fig = gcf()
+        axes = fig.get_axes()
+        self.assertEqual(len(axes), 2)
+        close('all')
+
     @slow
     def test_scatter(self):
         _skip_if_no_scipy()
 
-        df = DataFrame(np.random.randn(100, 4))
         df = DataFrame(np.random.randn(100, 2))
         import pandas.tools.plotting as plt
 
@@ -919,7 +932,7 @@ def test_time_series_plot_color_kwargs(self):
     def test_time_series_plot_color_with_empty_kwargs(self):
         import matplotlib as mpl
         import matplotlib.pyplot as plt
-        
+
         def_colors = mpl.rcParams['axes.color_cycle']
 
         plt.close('all')

pandas/tools/plotting.py

@@ -2026,7 +2026,7 @@ def hist_series(self, by=None, ax=None, grid=True, xlabelsize=None,
     """
     import matplotlib.pyplot as plt
 
-    fig = kwds.get('figure', plt.gcf()
+    fig = kwds.get('figure', _gcf()
                    if plt.get_fignums() else plt.figure(figsize=figsize))
     if figsize is not None and tuple(figsize) != tuple(fig.get_size_inches()):
         fig.set_size_inches(*figsize, forward=True)
@@ -2036,8 +2036,8 @@ def hist_series(self, by=None, ax=None, grid=True, xlabelsize=None,
             raise ValueError("The 'layout' keyword is not supported when "
                              "'by' is None")
         if ax is None:
-            ax = fig.add_subplot(111)
-        if ax.get_figure() != fig:
+            ax = fig.gca()
+        elif ax.get_figure() != fig:
             raise AssertionError('passed axis not bound to passed figure')
         values = self.dropna().values