BUG: xticks unnecessarily rotated (#34334)

Author: MarcoGorelli

doc/source/whatsnew/v1.2.0.rst

@@ -305,6 +305,7 @@ I/O
 Plotting
 ^^^^^^^^
 
+- Bug in :meth:`DataFrame.plot` was rotating xticklabels when ``subplots=True``, even if the x-axis wasn't an irregular time series (:issue:`29460`)
 - Bug in :meth:`DataFrame.plot` where a marker letter in the ``style`` keyword sometimes causes a ``ValueError`` (:issue:`21003`)
 
 Groupby/resample/rolling

pandas/plotting/_matplotlib/core.py

@@ -1231,11 +1231,15 @@ def get_label(i):
             ax.xaxis.set_major_locator(FixedLocator(xticks))
             ax.set_xticklabels(xticklabels)
 
+        # If the index is an irregular time series, then by default
+        # we rotate the tick labels. The exception is if there are
+        # subplots which don't share their x-axes, in which we case
+        # we don't rotate the ticklabels as by default the subplots
+        # would be too close together.
         condition = (
             not self._use_dynamic_x()
-            and data.index.is_all_dates
-            and not self.subplots
-            or (self.subplots and self.sharex)
+            and (data.index.is_all_dates and self.use_index)
+            and (not self.subplots or (self.subplots and self.sharex))
         )
 
         index_name = self._get_index_name()

pandas/tests/plotting/test_datetimelike.py

@@ -9,7 +9,7 @@
 from pandas._libs.tslibs import BaseOffset, to_offset
 import pandas.util._test_decorators as td
 
-from pandas import DataFrame, Index, NaT, Series, isna
+from pandas import DataFrame, Index, NaT, Series, isna, to_datetime
 import pandas._testing as tm
 from pandas.core.indexes.datetimes import DatetimeIndex, bdate_range, date_range
 from pandas.core.indexes.period import Period, PeriodIndex, period_range
@@ -1494,6 +1494,32 @@ def test_matplotlib_scatter_datetime64(self):
             expected = "2017-12-12"
         assert label.get_text() == expected
 
+    def test_check_xticks_rot(self):
+        # https://github.com/pandas-dev/pandas/issues/29460
+        # regular time series
+        x = to_datetime(["2020-05-01", "2020-05-02", "2020-05-03"])
+        df = DataFrame({"x": x, "y": [1, 2, 3]})
+        axes = df.plot(x="x", y="y")
+        self._check_ticks_props(axes, xrot=0)
+
+        # irregular time series
+        x = to_datetime(["2020-05-01", "2020-05-02", "2020-05-04"])
+        df = DataFrame({"x": x, "y": [1, 2, 3]})
+        axes = df.plot(x="x", y="y")
+        self._check_ticks_props(axes, xrot=30)
+
+        # use timeseries index or not
+        axes = df.set_index("x").plot(y="y", use_index=True)
+        self._check_ticks_props(axes, xrot=30)
+        axes = df.set_index("x").plot(y="y", use_index=False)
+        self._check_ticks_props(axes, xrot=0)
+
+        # separate subplots
+        axes = df.plot(x="x", y="y", subplots=True, sharex=True)
+        self._check_ticks_props(axes, xrot=30)
+        axes = df.plot(x="x", y="y", subplots=True, sharex=False)
+        self._check_ticks_props(axes, xrot=0)
+
 
 def _check_plot_works(f, freq=None, series=None, *args, **kwargs):
     import matplotlib.pyplot as plt

pandas/tests/plotting/test_frame.py

@@ -48,7 +48,6 @@ def _assert_xtickslabels_visibility(self, axes, expected):
         for ax, exp in zip(axes, expected):
             self._check_visible(ax.get_xticklabels(), visible=exp)
 
-    @pytest.mark.xfail(reason="Waiting for PR 34334", strict=True)
     @pytest.mark.slow
     def test_plot(self):
         from pandas.plotting._matplotlib.compat import mpl_ge_3_1_0
@@ -66,6 +65,7 @@ def test_plot(self):
 
         with tm.assert_produces_warning(UserWarning):
             axes = _check_plot_works(df.plot, subplots=True, use_index=False)
+        self._check_ticks_props(axes, xrot=0)
         self._check_axes_shape(axes, axes_num=4, layout=(4, 1))
 
         df = DataFrame({"x": [1, 2], "y": [3, 4]})
@@ -78,7 +78,8 @@ def test_plot(self):
 
         df = DataFrame(np.random.rand(10, 3), index=list(string.ascii_letters[:10]))
 
-        _check_plot_works(df.plot, use_index=True)
+        ax = _check_plot_works(df.plot, use_index=True)
+        self._check_ticks_props(ax, xrot=0)
         _check_plot_works(df.plot, sort_columns=False)
         _check_plot_works(df.plot, yticks=[1, 5, 10])
         _check_plot_works(df.plot, xticks=[1, 5, 10])
@@ -110,7 +111,8 @@ def test_plot(self):
 
         tuples = zip(string.ascii_letters[:10], range(10))
         df = DataFrame(np.random.rand(10, 3), index=MultiIndex.from_tuples(tuples))
-        _check_plot_works(df.plot, use_index=True)
+        ax = _check_plot_works(df.plot, use_index=True)
+        self._check_ticks_props(ax, xrot=0)
 
         # unicode
         index = MultiIndex.from_tuples(
@@ -304,12 +306,14 @@ def test_xcompat(self):
         ax = df.plot(x_compat=True)
         lines = ax.get_lines()
         assert not isinstance(lines[0].get_xdata(), PeriodIndex)
+        self._check_ticks_props(ax, xrot=30)
 
         tm.close()
         pd.plotting.plot_params["xaxis.compat"] = True
         ax = df.plot()
         lines = ax.get_lines()
         assert not isinstance(lines[0].get_xdata(), PeriodIndex)
+        self._check_ticks_props(ax, xrot=30)
 
         tm.close()
         pd.plotting.plot_params["x_compat"] = False
@@ -325,12 +329,14 @@ def test_xcompat(self):
             ax = df.plot()
             lines = ax.get_lines()
             assert not isinstance(lines[0].get_xdata(), PeriodIndex)
+            self._check_ticks_props(ax, xrot=30)
 
         tm.close()
         ax = df.plot()
         lines = ax.get_lines()
         assert not isinstance(lines[0].get_xdata(), PeriodIndex)
         assert isinstance(PeriodIndex(lines[0].get_xdata()), PeriodIndex)
+        self._check_ticks_props(ax, xrot=0)
 
     def test_period_compat(self):
         # GH 9012
@@ -486,7 +492,6 @@ def test_groupby_boxplot_sharex(self):
         expected = [False, False, True, True]
         self._assert_xtickslabels_visibility(axes, expected)
 
-    @pytest.mark.xfail(reason="Waiting for PR 34334", strict=True)
     @pytest.mark.slow
     def test_subplots_timeseries(self):
         idx = date_range(start="2014-07-01", freq="M", periods=10)

pandas/tests/plotting/test_series.py

@@ -109,6 +109,7 @@ def test_ts_area_lim(self):
         line = ax.get_lines()[0].get_data(orig=False)[0]
         assert xmin <= line[0]
         assert xmax >= line[-1]
+        self._check_ticks_props(ax, xrot=0)
         tm.close()
 
         # GH 7471
@@ -118,6 +119,7 @@ def test_ts_area_lim(self):
         line = ax.get_lines()[0].get_data(orig=False)[0]
         assert xmin <= line[0]
         assert xmax >= line[-1]
+        self._check_ticks_props(ax, xrot=30)
         tm.close()
 
         tz_ts = self.ts.copy()
@@ -128,6 +130,7 @@ def test_ts_area_lim(self):
         line = ax.get_lines()[0].get_data(orig=False)[0]
         assert xmin <= line[0]
         assert xmax >= line[-1]
+        self._check_ticks_props(ax, xrot=0)
         tm.close()
 
         _, ax = self.plt.subplots()
@@ -136,6 +139,7 @@ def test_ts_area_lim(self):
         line = ax.get_lines()[0].get_data(orig=False)[0]
         assert xmin <= line[0]
         assert xmax >= line[-1]
+        self._check_ticks_props(ax, xrot=0)
 
     def test_label(self):
         s = Series([1, 2])
@@ -284,6 +288,7 @@ def test_irregular_datetime(self):
         xp = DatetimeConverter.convert(datetime(1999, 1, 1), "", ax)
         ax.set_xlim("1/1/1999", "1/1/2001")
         assert xp == ax.get_xlim()[0]
+        self._check_ticks_props(ax, xrot=30)
 
     def test_unsorted_index_xlim(self):
         ser = Series(