BUG: Enable plotting with PeriodIndex with arbitrary frequencies, resolves #14763 (#26241)

* BUG: Enable plotting with PeriodIndex with arbitrary frequencies, resolves #14763

Author: JoElfner

doc/source/whatsnew/v0.25.0.rst

@@ -474,6 +474,8 @@ Plotting
 - Fixed bug where :class:`api.extensions.ExtensionArray` could not be used in matplotlib plotting (:issue:`25587`)
 - Bug in an error message in :meth:`DataFrame.plot`. Improved the error message if non-numerics are passed to :meth:`DataFrame.plot` (:issue:`25481`)
 - Bug in incorrect ticklabel positions when plotting an index that are non-numeric / non-datetime (:issue:`7612` :issue:`15912` :issue:`22334`)
+- Fixed bug causing plots of :class:`PeriodIndex` timeseries to fail if the frequency is a multiple of the frequency rule code (:issue:`14763`)
+-
 -
 -
 

pandas/plotting/_timeseries.py

@@ -262,7 +262,7 @@ def _get_index_freq(data):
 def _maybe_convert_index(ax, data):
     # tsplot converts automatically, but don't want to convert index
     # over and over for DataFrames
-    if isinstance(data.index, ABCDatetimeIndex):
+    if isinstance(data.index, (ABCDatetimeIndex, ABCPeriodIndex)):
         freq = getattr(data.index, 'freq', None)
 
         if freq is None:
@@ -279,7 +279,10 @@ def _maybe_convert_index(ax, data):
         freq = get_base_alias(freq)
         freq = frequencies.get_period_alias(freq)
 
-        data = data.to_period(freq=freq)
+        if isinstance(data.index, ABCDatetimeIndex):
+            data = data.to_period(freq=freq)
+        elif isinstance(data.index, ABCPeriodIndex):
+            data.index = data.index.asfreq(freq=freq)
     return data
 
 

pandas/tests/plotting/test_datetimelike.py

@@ -26,8 +26,9 @@ class TestTSPlot(TestPlotBase):
     def setup_method(self, method):
         TestPlotBase.setup_method(self, method)
 
-        freq = ['S', 'T', 'H', 'D', 'W', 'M', 'Q', 'A']
-        idx = [period_range('12/31/1999', freq=x, periods=100) for x in freq]
+        self.freq = ['S', 'T', 'H', 'D', 'W', 'M', 'Q', 'A']
+        idx = [
+            period_range('12/31/1999', freq=x, periods=100) for x in self.freq]
         self.period_ser = [Series(np.random.randn(len(x)), x) for x in idx]
         self.period_df = [DataFrame(np.random.randn(len(x), 3), index=x,
                                     columns=['A', 'B', 'C'])
@@ -209,6 +210,16 @@ def test_line_plot_period_series(self):
         for s in self.period_ser:
             _check_plot_works(s.plot, s.index.freq)
 
+    @pytest.mark.slow
+    @pytest.mark.parametrize(
+        'frqncy', ['1S', '3S', '5T', '7H', '4D', '8W', '11M', '3A'])
+    def test_line_plot_period_mlt_series(self, frqncy):
+        # test period index line plot for series with multiples (`mlt`) of the
+        # frequency (`frqncy`) rule code. tests resolution of issue #14763
+        idx = period_range('12/31/1999', freq=frqncy, periods=100)
+        s = Series(np.random.randn(len(idx)), idx)
+        _check_plot_works(s.plot, s.index.freq.rule_code)
+
     @pytest.mark.slow
     def test_line_plot_datetime_series(self):
         for s in self.datetime_ser:
@@ -219,6 +230,19 @@ def test_line_plot_period_frame(self):
         for df in self.period_df:
             _check_plot_works(df.plot, df.index.freq)
 
+    @pytest.mark.slow
+    @pytest.mark.parametrize(
+        'frqncy', ['1S', '3S', '5T', '7H', '4D', '8W', '11M', '3A'])
+    def test_line_plot_period_mlt_frame(self, frqncy):
+        # test period index line plot for DataFrames with multiples (`mlt`)
+        # of the frequency (`frqncy`) rule code. tests resolution of issue
+        # #14763
+        idx = period_range('12/31/1999', freq=frqncy, periods=100)
+        df = DataFrame(np.random.randn(len(idx), 3), index=idx,
+                       columns=['A', 'B', 'C'])
+        freq = df.index.asfreq(df.index.freq.rule_code).freq
+        _check_plot_works(df.plot, freq)
+
     @pytest.mark.slow
     def test_line_plot_datetime_frame(self):
         for df in self.datetime_df: