BUG: Handle overlapping line and bar on the same plot #61173

MartinBraquet · 2025-03-24T09:22:19Z

closes BUG: fails to plot 2 plots with secondary y axis when index type is PeriodIndex and plot kinds are different #61161
Tests added and passed if fixing a bug or adding a new feature
All code checks passed.
Added type annotations to new arguments/methods/functions.
Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

This code

import pandas as pd
import matplotlib.pyplot as plt

index = pd.period_range('2023', periods=3, freq='Y')
df = pd.DataFrame({
    'col1': [10, 20, 30],
    'col2': [40, 25, 10]
}, index=index)

fig, ax = plt.subplots()
df['col1'].plot(kind='bar', ax=ax)
ax2 = ax.twinx()
df['col2'].plot(kind='line', ax=ax2, color = 'r')
plt.show()

from the linked issue gives this plot:

And swapping the lines (line before bar)

df['col2'].plot(kind='line', ax=ax2, color = 'r')
df['col1'].plot(kind='bar', ax=ax)

gives

I believe the difference of results stems from the fact that the figure is always cropped to match the x-range of the last plot. We can certainly adjust the PR to make the first figure behave like the second one if desired.

Please provide feedback on the overall approach. Once confirmed, I'll expand and cover with tests.

rhshadrach

Thanks for the PR! Can you add a test in pandas/tests/plotting/test_series.py. Make the plots and check that the x-axis is as expected.

pandas/plotting/_matplotlib/core.py

Introduce `convert_from_freq` method and streamline the conversion process by passing `freq` directly instead of using `axis.freq`. This improves modularity and ensures clearer separation of concerns for frequency handling in Period conversion.

Simplified `tick_pos` calculation by reusing helper methods and added a decorator to register pandas Matplotlib converters in the `_plot` method. This improves clarity and ensures proper integration with the pandas Matplotlib ecosystem.

This test ensures that bar and line plots with identical x values are correctly superposed on the same axes. It verifies that the x-tick positions remain consistent across plot types.

MartinBraquet · 2025-04-07T15:48:58Z

pandas/tests/plotting/test_series.py

@@ -971,3 +971,17 @@ def test_secondary_y_subplot_axis_labels(self):
        s1.plot(ax=ax2)
        assert len(ax.xaxis.get_minor_ticks()) == 0
        assert len(ax.get_xticklabels()) > 0
+
+    def test_bar_line_plot(self):


Fails on main

Resolved a bug that prevented a line and bar from aligning on the same plot in `Series.plot`. This addresses issue pandas-dev#61161 and improves plot consistency when combining these chart types.

Move `x_compat` logic and time series helper methods from `LinePlot` to `MPLPlot` for better reusability and maintainability. This simplifies the `LinePlot` class and centralizes common functionality.

MartinBraquet · 2025-04-07T16:25:22Z

pandas/plotting/_matplotlib/converter.py

+        return PeriodConverter.convert_from_freq(values, axis.freq)
+
+    @staticmethod
+    def convert_from_freq(values, freq):


convert only uses the freq attribute of axis, so one should allow the user to pass freq without axis object.

MartinBraquet · 2025-04-07T16:27:09Z

pandas/plotting/_matplotlib/core.py

+        from pandas.plotting import plot_params
+
+        self.x_compat = plot_params["x_compat"]
+        if "x_compat" in self.kwds:
+            self.x_compat = bool(self.kwds.pop("x_compat"))
+
+    @final
+    def _is_ts_plot(self) -> bool:
+        # this is slightly deceptive
+        return not self.x_compat and self.use_index and self._use_dynamic_x()
+
+    @final
+    def _use_dynamic_x(self) -> bool:
+        return use_dynamic_x(self._get_ax(0), self.data)
+


Those routines are not exclusive to LinePlot, as they seem related to any type of time series. _is_ts_plot is used in this PR to check if a boxplot is a time series.

MartinBraquet · 2025-04-07T16:28:18Z

@rhshadrach I covered the change with a test. I believe the PR is now ready for review and then merge.

doc/source/whatsnew/v3.0.0.rst

pandas/tests/plotting/test_series.py

# Conflicts: # doc/source/whatsnew/v3.0.0.rst # pandas/plotting/_matplotlib/core.py

Ensure bar and line plots share consistent x-axis tick labels and verify that x-axis limits are adjusted to make all plotted elements visible in `test_bar_line_plot` test. These changes improve the robustness of visual alignment and boundary checks.

Add an assertion to verify the length of `bar_xticks` aligns with the length of the index. This improves the test's robustness by ensuring the data and ticks remain consistent.

MartinBraquet · 2025-04-14T04:37:31Z

pandas/tests/plotting/test_series.py

+        assert len(bar_xticks) == len(index)
+        assert bar_xticks == line_xticks


This is checking that

the three index years are in the two plots

the x-tick positions for those years are the same in the two plots

MartinBraquet · 2025-04-14T04:38:44Z

pandas/tests/plotting/test_series.py

+        assert x_limits[0] <= bar_xticks[0].get_position()[0]
+        assert x_limits[1] >= bar_xticks[-1].get_position()[0]


Check that both left-most and right-most data points are shown in the current view

rhshadrach

lgtm

MartinBraquet · 2025-04-18T10:49:22Z

Only a maintainer is allowed to merge a PR, right?

mroeschke · 2025-04-18T16:12:53Z

Thanks @MartinBraquet

Handle line and box on the same plot

3caf8e6

MartinBraquet changed the title ~~BUG: Handle line and box on the same plot~~ BUG: Handle line and bar on the same plot Mar 24, 2025

MartinBraquet mentioned this pull request Mar 24, 2025

BUG: fails to plot 2 plots with secondary y axis when index type is PeriodIndex and plot kinds are different #61161

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Handle line and box on the same plot

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rhshadrach added Bug Visualization labels Mar 26, 2025

MartinBraquet added 3 commits April 7, 2025 22:34

Add test for bar and line plot superposition with same x values

e5b4e6f

This test ensures that bar and line plots with identical x values are correctly superposed on the same axes. It verifies that the x-tick positions remain consistent across plot types.

MartinBraquet commented Apr 7, 2025

View reviewed changes

MartinBraquet changed the title ~~BUG: Handle line and bar on the same plot~~ BUG: Handle overlapping line and bar on the same plot Apr 7, 2025

MartinBraquet added 3 commits April 7, 2025 22:56

Merge branch 'main' into plot

c5a6554

Fix alignment issue in Series.plot with line and bar.

218871d

Resolved a bug that prevented a line and bar from aligning on the same plot in `Series.plot`. This addresses issue pandas-dev#61161 and improves plot consistency when combining these chart types.

Refactor time series handling in matplotlib plotting.

16762b6

Move `x_compat` logic and time series helper methods from `LinePlot` to `MPLPlot` for better reusability and maintainability. This simplifies the `LinePlot` class and centralizes common functionality.

MartinBraquet commented Apr 7, 2025

View reviewed changes

MartinBraquet mentioned this pull request Apr 7, 2025

BUG: Handle overlapping line and scatter on the same plot #61244

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Merge branch 'main' into plot

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MartinBraquet requested a review from rhshadrach April 8, 2025 04:29

MartinBraquet added 2 commits April 8, 2025 11:29

Merge branch 'main' into plot

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Merge branch 'main' into plot

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MartinBraquet commented Apr 9, 2025

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Update doc/source/whatsnew/v3.0.0.rst

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Apply suggestions from code review

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# Conflicts: # doc/source/whatsnew/v3.0.0.rst # pandas/plotting/_matplotlib/core.py

MartinBraquet added 3 commits April 14, 2025 11:18

Merge remote-tracking branch 'origin/plot' into plot

168b271

Ensure bar_xticks length matches index in test_series.py

5cc8c28

Add an assertion to verify the length of `bar_xticks` aligns with the length of the index. This improves the test's robustness by ensuring the data and ticks remain consistent.

MartinBraquet commented Apr 14, 2025

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rhshadrach added this to the 3.0 milestone Apr 16, 2025

Merge branch 'main' into plot

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mroeschke merged commit 5f354ca into pandas-dev:main Apr 18, 2025
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BUG: Handle overlapping line and bar on the same plot #61173

BUG: Handle overlapping line and bar on the same plot #61173

MartinBraquet commented Mar 24, 2025 •

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mroeschke commented Apr 18, 2025

		assert len(bar_xticks) == len(index)
		assert bar_xticks == line_xticks

		assert x_limits[0] <= bar_xticks[0].get_position()[0]
		assert x_limits[1] >= bar_xticks[-1].get_position()[0]

BUG: Handle overlapping line and bar on the same plot #61173

BUG: Handle overlapping line and bar on the same plot #61173

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