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Matplotlib deprecation warning #183

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roryyorke opened this issue Jan 6, 2018 · 1 comment
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Matplotlib deprecation warning #183

roryyorke opened this issue Jan 6, 2018 · 1 comment
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enhancement
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0.8.0

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@roryyorke
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see, e.g.,

https://travis-ci.org/python-control/python-control/jobs/325460249#L2815

The warning says:

test_siso (control.tests.freqresp_test.TestFreqresp) ... /home/travis/miniconda/envs/test-environment/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
@murrayrm murrayrm added this to the 0.8.0 milestone Jan 6, 2018
@murrayrm murrayrm mentioned this issue Jan 15, 2018
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This has been fixed in PR #187. The issue is a planned change in the behavior of the matplotlib axes command (which is called by matplotlib.subplot in control.bode_plot and control.gangof4_plot). In the old behavior, if you called axes or subplot with the same argument, you got a pointer to the previous object. This behavior is not desired and so it is being deprecated. Details in matplotlib PR #9037.

What generated this behavior in the test suit was that we called bode twice in a row in the unit test and this caused matplotlib.pyplot.subfig to get called with the same arguments. The fix was to add a randomly generated internal "label" (not displayed anywhere), as described in the warning message.

@murrayrm murrayrm closed this as completed Feb 5, 2018
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