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[Bug]: Axes.cla() with sharex may wrongly reset the axes limit. #27825

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tianzhuqiao opened this issue Feb 27, 2024 · 1 comment · May be fixed by #28101
Open

[Bug]: Axes.cla() with sharex may wrongly reset the axes limit. #27825

tianzhuqiao opened this issue Feb 27, 2024 · 1 comment · May be fixed by #28101
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topic: axes
Milestone
v3.10.0

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@tianzhuqiao
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Bug summary

For example, when subplot A shares the x-axis with subplot B (A is created with sharex=B), a call to B.cla() will set the xlimit to [0, 1], which may not be expected (in contrast, a call to A.cla() will not change the xlimit).

I think the main problem comes from the following function, where it will check whether its _sharex attribute is None; however, in this case, B is shared to A, but no axis is shared to B, so B's _sharex attribute is None.

matplotlib/lib/matplotlib/axes/_base.py

Line 1369 in 9e18a34

if share is not None:

Code for reproduction

ax = plt.subplot(211)
ax2 = plt.subplot(212, sharex=ax)
ax.plot(range(50))
ax2.plot(range(50))
ax.cla()
plt.show()

Actual outcome

image

Expected outcome

image

Additional information

No response

Operating system

No response

Matplotlib Version

3.8.3

Matplotlib Backend

'TkAgg'

Python version

3.9.13

Jupyter version

No response

Installation

pip
@JamesCamilleri13
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Hi,
I suggest that if A shares an axis with B, then B should also have his sharex/sharey attribute changed.

The following modification in the lib/matplotlib/axes/_base.py file solves your issue.

diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
index 12dace5b00..874e30e9e5 100644
--- a/lib/matplotlib/axes/_base.py
+++ b/lib/matplotlib/axes/_base.py
@@ -1233,8 +1233,8 @@ class _AxesBase(martist.Artist):
         x0, x1 = other.get_xlim()
         self.set_xlim(x0, x1, emit=False, auto=other.get_autoscalex_on())
         self.xaxis._scale = other.xaxis._scale
+        other._shared_axes["x"].join(other, self)
+        other._sharex = self

     def sharey(self, other):
         """
@@ -1254,8 +1254,8 @@ class _AxesBase(martist.Artist):
         y0, y1 = other.get_ylim()
         self.set_ylim(y0, y1, emit=False, auto=other.get_autoscaley_on())
         self.yaxis._scale = other.yaxis._scale
+        other._shared_axes["y"].join(other, self)
+        other._sharey = self

     def __clear(self):
         """Clear the Axes."""
@@ -1374,7 +1374,7 @@ class _AxesBase(martist.Artist):
             share = getattr(self, f"_share{name}")
             if share is not None:
 		 getattr(self, f"share{name}")(share)
+                axis.set_inverted(False)
             else:
                 # Although the scale was set to linear as part of clear,
                 # polar requires that _set_scale is called again

After running tests , i noticed that we also have to manually invert any inverted axis when clearing a subplot

@JamesCamilleri13 JamesCamilleri13 linked a pull request Apr 18, 2024 that will close this issue
Open
@tacaswell tacaswell added this to the v3.10.0 milestone Apr 19, 2024
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Fixed xlim issue when clearing shared axes JamesCamilleri13/matplotlib
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@tacaswell @dstansby @tianzhuqiao @JamesCamilleri13