ENH: Add the ability to have a separate title for each subplot when plotting

doc/source/whatsnew/v0.20.0.txt

@@ -40,7 +40,7 @@ Other enhancements
 ^^^^^^^^^^^^^^^^^^
 
 - ``pd.read_excel`` now preserves sheet order when using ``sheetname=None`` (:issue:`9930`)
-
+- ``pd.DataFrame.plot`` now prints a title above each subplot if ``suplots=True`` and ``title`` is a list of strings
 
 .. _whatsnew_0200.api_breaking:
 

pandas/tests/plotting/test_misc.py

@@ -16,13 +16,11 @@
 from pandas.tests.plotting.common import (TestPlotBase, _check_plot_works,
                                           _ok_for_gaussian_kde)
 
-
 """ Test cases for misc plot functions """
 
 
 @tm.mplskip
 class TestSeriesPlots(TestPlotBase):
-
     def setUp(self):
         TestPlotBase.setUp(self)
         import matplotlib as mpl
@@ -54,7 +52,6 @@ def test_bootstrap_plot(self):
 
 @tm.mplskip
 class TestDataFramePlots(TestPlotBase):
-
     @slow
     def test_scatter_plot_legacy(self):
         tm._skip_if_no_scipy()
@@ -277,6 +274,26 @@ def test_radviz(self):
         handles, labels = ax.get_legend_handles_labels()
         self._check_colors(handles, facecolors=colors)
 
+    @slow
+    def test_subplot_titles(self):
+        df = self.iris.drop('Name', axis=1).head()
+        # Use the column names as the subplot titles
+        title = list(df.columns)
+
+        # Case len(title) == len(df)
+        plot = df.plot(subplots=True, title=title)
+        self.assertEqual([p.title._text for p in plot], title)
+
+        # Case len(title) > len(df)
+        self.assertRaises(ValueError, df.plot, subplots=True,
+                          title=title + ["kittens > puppies"])
+
+        # Case len(title) < len(df)
+        self.assertRaises(ValueError, df.plot, subplots=True, title=title[:2])
+
+        # Case subplots=False and title is of type list
+        self.assertRaises(ValueError, df.plot, subplots=False, title=title)
+
 
 if __name__ == '__main__':
     nose.runmodule(argv=[__file__, '-vvs', '-x', '--pdb', '--pdb-failure'],

pandas/tools/plotting.py

@@ -1217,8 +1217,22 @@ def _adorn_subplots(self):
 
         if self.title:
             if self.subplots:
-                self.fig.suptitle(self.title)
+                if is_list_like(self.title):
+                    if len(self.title) != len(self.axes):
+                        msg = 'The length of `title` must equal the number ' \
+                              'of columns if using `title` of type `list` ' \
+                              'and `subplots=True`'
+                        raise ValueError(msg)
+
+                    for (ax, title) in zip(self.axes, self.title):
+                        ax.set_title(title)
+                else:
+                    self.fig.suptitle(self.title)
             else:
+                if is_list_like(self.title):
+                    msg = 'Using `title` of type `list` is not supported ' \
+                          'unless `subplots=True` is passed'
+                    raise ValueError(msg)
                 self.axes[0].set_title(self.title)
 
     def _apply_axis_properties(self, axis, rot=None, fontsize=None):
@@ -2555,8 +2569,10 @@ def _plot(data, x=None, y=None, subplots=False,
     figsize : a tuple (width, height) in inches
     use_index : boolean, default True
         Use index as ticks for x axis
-    title : string
-        Title to use for the plot
+    title : string or list
+        If a string is passed, print the string at the top of the figure. If a
+        list is passed and subplots is True, print each item in the
+        list above the corresponding subplot.
     grid : boolean, default None (matlab style default)
         Axis grid lines
     legend : False/True/'reverse'