BUG: secondary ax has incorrect right_ax property

doc/source/whatsnew/v0.16.1.txt

@@ -110,6 +110,7 @@ Bug Fixes
 
 - Bug in ``DataFrame.plot(kind="hist")`` results in ``TypeError`` when ``DataFrame`` contains non-numeric columns (:issue:`9853`)
 - Bug where repeated plotting of ``DataFrame`` with a ``DatetimeIndex`` may raise ``TypeError`` (:issue:`9852`)
+- Bug in plotting ``secondary_y`` incorrectly attaches ``right_ax`` property to secondary axes specifying itself recursively. (:issue:`9861`)
 
 - Bug in ``Series.quantile`` on empty Series of type ``Datetime`` or ``Timedelta`` (:issue:`9675`)
 - Bug in ``where`` causing incorrect results when upcasting was required (:issue:`9731`)

pandas/tests/test_graphics.py

@@ -1609,7 +1609,10 @@ def test_line_lim(self):
  self.assertEqual(xmax, lines[0].get_data()[0][-1])
 
  axes = df.plot(secondary_y=True, subplots=True)
+ self._check_axes_shape(axes, axes_num=3, layout=(3, 1))
  for ax in axes:
+ self.assertTrue(hasattr(ax, 'left_ax'))
+ self.assertFalse(hasattr(ax, 'right_ax'))
  xmin, xmax = ax.get_xlim()
  lines = ax.get_lines()
  self.assertEqual(xmin, lines[0].get_data()[0][0])

pandas/tools/plotting.py

@@ -927,19 +927,21 @@ def _has_plotted_object(self, ax):
 
  def _maybe_right_yaxis(self, ax, axes_num):
  if not self.on_right(axes_num):
- if hasattr(ax, 'left_ax'):
- # secondary axes may be passed as axes
- return ax.left_ax
- return ax
+ # secondary axes may be passed via ax kw
+ return self._get_ax_layer(ax)
 
  if hasattr(ax, 'right_ax'):
+ # if it has right_ax proparty, ``ax`` must be left axes
  return ax.right_ax
+ elif hasattr(ax, 'left_ax'):
+ # if it has left_ax proparty, ``ax`` must be right axes
+ return ax
  else:
+ # otherwise, create twin axes
  orig_ax, new_ax = ax, ax.twinx()
  new_ax._get_lines.color_cycle = orig_ax._get_lines.color_cycle
 
  orig_ax.right_ax, new_ax.left_ax = new_ax, orig_ax
- new_ax.right_ax = new_ax
 
  if not self._has_plotted_object(orig_ax): # no data on left y
  orig_ax.get_yaxis().set_visible(False)
@@ -987,9 +989,8 @@ def result(self):
  all_sec = (com.is_list_like(self.secondary_y) and
  len(self.secondary_y) == self.nseries)
  if (sec_true or all_sec):
- # if all data is plotted on secondary,
- # return secondary axes
- return self.axes[0].right_ax
+ # if all data is plotted on secondary, return right axes
+ return self._get_ax_layer(self.axes[0], primary=False)
  else:
  return self.axes[0]
 
@@ -1229,11 +1230,18 @@ def _get_index_name(self):
 
  return name
 
+ @classmethod
+ def _get_ax_layer(cls, ax, primary=True):
+ """get left (primary) or right (secondary) axes"""
+ if primary:
+ return getattr(ax, 'left_ax', ax)
+ else:
+ return getattr(ax, 'right_ax', ax)
+
  def _get_ax(self, i):
  # get the twinx ax if appropriate
  if self.subplots:
  ax = self.axes[i]
-
  ax = self._maybe_right_yaxis(ax, i)
  self.axes[i] = ax
  else:
@@ -2500,8 +2508,7 @@ def plot_series(data, kind='line', ax=None, # Series unique
  """
  if ax is None and len(plt.get_fignums()) > 0:
  ax = _gca()
- ax = getattr(ax, 'left_ax', ax)
-
+ ax = MPLPlot._get_ax_layer(ax)
  return _plot(data, kind=kind, ax=ax,
  figsize=figsize, use_index=use_index, title=title,
  grid=grid, legend=legend,
@@ -3348,11 +3355,9 @@ def _flatten(axes):
 def _get_all_lines(ax):
  lines = ax.get_lines()
 
- # check for right_ax, which can oddly sometimes point back to ax
- if hasattr(ax, 'right_ax') and ax.right_ax != ax:
+ if hasattr(ax, 'right_ax'):
  lines += ax.right_ax.get_lines()
 
- # no such risk with left_ax
  if hasattr(ax, 'left_ax'):
  lines += ax.left_ax.get_lines()
 

pandas/tseries/tests/test_plotting.py

@@ -528,7 +528,9 @@ def test_secondary_y(self):
 
  ser = Series(np.random.randn(10))
  ser2 = Series(np.random.randn(10))
- ax = ser.plot(secondary_y=True).right_ax
+ ax = ser.plot(secondary_y=True)
+ self.assertTrue(hasattr(ax, 'left_ax'))
+ self.assertFalse(hasattr(ax, 'right_ax'))
  fig = ax.get_figure()
  axes = fig.get_axes()
  l = ax.get_lines()[0]
@@ -543,16 +545,22 @@ def test_secondary_y(self):
  plt.close(ax2.get_figure())
 
  ax = ser2.plot()
- ax2 = ser.plot(secondary_y=True).right_ax
+ ax2 = ser.plot(secondary_y=True)
  self.assertTrue(ax.get_yaxis().get_visible())
+ self.assertFalse(hasattr(ax, 'left_ax'))
+ self.assertTrue(hasattr(ax, 'right_ax'))
+ self.assertTrue(hasattr(ax2, 'left_ax'))
+ self.assertFalse(hasattr(ax2, 'right_ax'))
 
  @slow
  def test_secondary_y_ts(self):
  import matplotlib.pyplot as plt
  idx = date_range('1/1/2000', periods=10)
  ser = Series(np.random.randn(10), idx)
  ser2 = Series(np.random.randn(10), idx)
- ax = ser.plot(secondary_y=True).right_ax
+ ax = ser.plot(secondary_y=True)
+ self.assertTrue(hasattr(ax, 'left_ax'))
+ self.assertFalse(hasattr(ax, 'right_ax'))
  fig = ax.get_figure()
  axes = fig.get_axes()
  l = ax.get_lines()[0]
@@ -577,7 +585,9 @@ def test_secondary_kde(self):
 
  import matplotlib.pyplot as plt
  ser = Series(np.random.randn(10))
- ax = ser.plot(secondary_y=True, kind='density').right_ax
+ ax = ser.plot(secondary_y=True, kind='density')
+ self.assertTrue(hasattr(ax, 'left_ax'))
+ self.assertFalse(hasattr(ax, 'right_ax'))
  fig = ax.get_figure()
  axes = fig.get_axes()
  self.assertEqual(axes[1].get_yaxis().get_ticks_position(), 'right')
@@ -922,7 +932,9 @@ def test_secondary_upsample(self):
  ax = high.plot(secondary_y=True)
  for l in ax.get_lines():
  self.assertEqual(PeriodIndex(l.get_xdata()).freq, 'D')
- for l in ax.right_ax.get_lines():
+ self.assertTrue(hasattr(ax, 'left_ax'))
+ self.assertFalse(hasattr(ax, 'right_ax'))
+ for l in ax.left_ax.get_lines():
  self.assertEqual(PeriodIndex(l.get_xdata()).freq, 'D')
 
  @slow