Backport PR #39235: Revert "Inconsistent indexes for tick label plotting (#28733)" (#39252)

Co-authored-by: Simon Hawkins <[email protected]>

Author: meeseeksmachine

doc/source/whatsnew/v1.2.0.rst

@@ -751,7 +751,7 @@ 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 caused a ``ValueError`` (:issue:`21003`)
-- Bug in :meth:`DataFrame.plot.bar` and :meth:`Series.plot.bar` where ticks positions were assigned by value order instead of using the actual value for numeric or a smart ordering for string (:issue:`26186`, :issue:`11465`)
+- Bug in :meth:`DataFrame.plot.bar` and :meth:`Series.plot.bar` where ticks positions were assigned by value order instead of using the actual value for numeric or a smart ordering for string (:issue:`26186`, :issue:`11465`). This fix has been reverted in pandas 1.2.1, see :doc:`v1.2.1`
 - Twinned axes were losing their tick labels which should only happen to all but the last row or column of 'externally' shared axes (:issue:`33819`)
 - Bug in :meth:`Series.plot` and :meth:`DataFrame.plot` was throwing a :exc:`ValueError` when the Series or DataFrame was
   indexed by a :class:`.TimedeltaIndex` with a fixed frequency and the x-axis lower limit was greater than the upper limit (:issue:`37454`)

doc/source/whatsnew/v1.2.1.rst

@@ -34,6 +34,9 @@ Fixed regressions
 - Fixed regression that raised ``AttributeError`` with PyArrow versions [0.16.0, 1.0.0) (:issue:`38801`)
 - Fixed regression in :func:`pandas.testing.assert_frame_equal` raising ``TypeError`` with ``check_like=True`` when :class:`Index` or columns have mixed dtype (:issue:`39168`)
 
+We have reverted a commit that resulted in several plotting related regressions in pandas 1.2.0 (:issue:`38969`, :issue:`38736`, :issue:`38865`, :issue:`38947` and :issue:`39126`).
+As a result, bugs reported as fixed in pandas 1.2.0 related to inconsistent tick labeling in bar plots are again present (:issue:`26186` and :issue:`11465`)
+
 .. ---------------------------------------------------------------------------
 
 .. _whatsnew_121.bug_fixes:

pandas/plotting/_matplotlib/core.py

@@ -1370,6 +1370,7 @@ def __init__(self, data, **kwargs):
         self.bar_width = kwargs.pop("width", 0.5)
         pos = kwargs.pop("position", 0.5)
         kwargs.setdefault("align", "center")
+        self.tick_pos = np.arange(len(data))
 
         self.bottom = kwargs.pop("bottom", 0)
         self.left = kwargs.pop("left", 0)
@@ -1392,16 +1393,7 @@ def __init__(self, data, **kwargs):
                 self.tickoffset = self.bar_width * pos
                 self.lim_offset = 0
 
-        if isinstance(self.data.index, ABCMultiIndex):
-            if kwargs["ax"] is not None and kwargs["ax"].has_data():
-                warnings.warn(
-                    "Redrawing a bar plot with a MultiIndex is not supported "
-                    + "and may lead to inconsistent label positions.",
-                    UserWarning,
-                )
-            self.ax_index = np.arange(len(data))
-        else:
-            self.ax_index = self.data.index
+        self.ax_pos = self.tick_pos - self.tickoffset
 
     def _args_adjust(self):
         if is_list_like(self.bottom):
@@ -1428,15 +1420,6 @@ def _make_plot(self):
 
         for i, (label, y) in enumerate(self._iter_data(fillna=0)):
             ax = self._get_ax(i)
-
-            if self.orientation == "vertical":
-                ax.xaxis.update_units(self.ax_index)
-                self.tick_pos = ax.convert_xunits(self.ax_index).astype(np.int)
-            elif self.orientation == "horizontal":
-                ax.yaxis.update_units(self.ax_index)
-                self.tick_pos = ax.convert_yunits(self.ax_index).astype(np.int)
-            self.ax_pos = self.tick_pos - self.tickoffset
-
             kwds = self.kwds.copy()
             if self._is_series:
                 kwds["color"] = colors
@@ -1508,8 +1491,8 @@ def _post_plot_logic(self, ax: "Axes", data):
             str_index = [pprint_thing(key) for key in range(data.shape[0])]
         name = self._get_index_name()
 
-        s_edge = self.ax_pos.min() - 0.25 + self.lim_offset
-        e_edge = self.ax_pos.max() + 0.25 + self.bar_width + self.lim_offset
+        s_edge = self.ax_pos[0] - 0.25 + self.lim_offset
+        e_edge = self.ax_pos[-1] + 0.25 + self.bar_width + self.lim_offset
 
         self._decorate_ticks(ax, name, str_index, s_edge, e_edge)
 

pandas/tests/plotting/frame/test_frame.py

@@ -2176,80 +2176,6 @@ def test_xlabel_ylabel_dataframe_plane_plot(self, kind, xlabel, ylabel):
         assert ax.get_xlabel() == (xcol if xlabel is None else xlabel)
         assert ax.get_ylabel() == (ycol if ylabel is None else ylabel)
 
-    @pytest.mark.parametrize("method", ["bar", "barh"])
-    def test_bar_ticklabel_consistence(self, method):
-        # Draw two consecutiv bar plot with consistent ticklabels
-        # The labels positions should not move between two drawing on the same axis
-        # GH: 26186
-        def get_main_axis(ax):
-            if method == "barh":
-                return ax.yaxis
-            elif method == "bar":
-                return ax.xaxis
-
-        # Plot the first bar plot
-        data = {"A": 0, "B": 3, "C": -4}
-        df = DataFrame.from_dict(data, orient="index", columns=["Value"])
-        ax = getattr(df.plot, method)()
-        ax.get_figure().canvas.draw()
-
-        # Retrieve the label positions for the first drawing
-        xticklabels = [t.get_text() for t in get_main_axis(ax).get_ticklabels()]
-        label_positions_1 = dict(zip(xticklabels, get_main_axis(ax).get_ticklocs()))
-
-        # Modify the dataframe order and values and plot on same axis
-        df = df.sort_values("Value") * -2
-        ax = getattr(df.plot, method)(ax=ax, color="red")
-        ax.get_figure().canvas.draw()
-
-        # Retrieve the label positions for the second drawing
-        xticklabels = [t.get_text() for t in get_main_axis(ax).get_ticklabels()]
-        label_positions_2 = dict(zip(xticklabels, get_main_axis(ax).get_ticklocs()))
-
-        # Assert that the label positions did not change between the plotting
-        assert label_positions_1 == label_positions_2
-
-    def test_bar_numeric(self):
-        # Bar plot with numeric index have tick location values equal to index
-        # values
-        # GH: 11465
-        df = DataFrame(np.random.rand(10), index=np.arange(10, 20))
-        ax = df.plot.bar()
-        ticklocs = ax.xaxis.get_ticklocs()
-        expected = np.arange(10, 20, dtype=np.int64)
-        tm.assert_numpy_array_equal(ticklocs, expected)
-
-    def test_bar_multiindex(self):
-        # Test from pandas/doc/source/user_guide/visualization.rst
-        # at section Plotting With Error Bars
-        # Related to issue GH: 26186
-
-        ix3 = pd.MultiIndex.from_arrays(
-            [
-                ["a", "a", "a", "a", "b", "b", "b", "b"],
-                ["foo", "foo", "bar", "bar", "foo", "foo", "bar", "bar"],
-            ],
-            names=["letter", "word"],
-        )
-
-        df3 = DataFrame(
-            {"data1": [3, 2, 4, 3, 2, 4, 3, 2], "data2": [6, 5, 7, 5, 4, 5, 6, 5]},
-            index=ix3,
-        )
-
-        # Group by index labels and take the means and standard deviations
-        # for each group
-        gp3 = df3.groupby(level=("letter", "word"))
-        means = gp3.mean()
-        errors = gp3.std()
-
-        # No assertion we just ensure that we can plot a MultiIndex bar plot
-        # and are getting a UserWarning if redrawing
-        with tm.assert_produces_warning(None):
-            ax = means.plot.bar(yerr=errors, capsize=4)
-        with tm.assert_produces_warning(UserWarning):
-            means.plot.bar(yerr=errors, capsize=4, ax=ax)
-
 
 def _generate_4_axes_via_gridspec():
     import matplotlib as mpl