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plt.bar() fails on 2D arrays with singleton dimensions. error message is unhelpful. #10733

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plt.bar() fails on 2D arrays with singleton dimensions. error message is unhelpful.#10733
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API: argument checkingValidation of acceptable argument valuesAPI: consistencyConsistency of the matplotlib API, including naming, behavior, defaults, …status: closed as inactiveIssues closed by the "Stale" Github Action. Please comment on any you think should still be open.status: inactiveMarked by the “Stale” Github Action
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future releases
@HoniSanders

Description

@HoniSanders
HoniSanders
opened on Mar 9, 2018

Bug report

Bug summary
plt.bar() only accept 1D arrays, and does not accept 2D arrays with a dimension that has length 1. E.g., does not accept arrays with shape (3,1). Unfortunately, the traceback is unhelpful.

Code for reproduction

from matplotlib import pyplot as plt
import numpy as np
plt.bar(np.zeros((2,)),np.zeros((2,1)))

Actual outcome

  File "<stdin>", line 1, in <module>
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/pyplot.py", line 2648, in bar
    ret = ax.bar(*args, **kwargs)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/__init__.py", line 1717, in inner
    return func(ax, *args, **kwargs)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/axes/_axes.py", line 2087, in bar
    label='_nolegend_',
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/patches.py", line 659, in __init__
    Patch.__init__(self, **kwargs)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/patches.py", line 103, in __init__
    self.set_linewidth(linewidth)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/patches.py", line 351, in set_linewidth
    self._linewidth = float(w)
TypeError: only length-1 arrays can be converted to Python scalars

Expected outcome

plt.bar() should be able to figure out that a 1D vector and a 2D array with a singleton dimension are equivalent. This can be done by applying squeeze if necessary. In any case if plt.bar() is going to fail unintuitively on this, it should test to see if the input is a 2D array, and provide an informative error message.

Matplotlib version

  • Operating system: windows, linux, and mac
  • Matplotlib version: most recent
  • Matplotlib backend (print(matplotlib.get_backend())):
  • Python version: 2.7 and 3.6
  • Jupyter version (if applicable):
  • Other libraries:

This code works with matplotlib version 1.4.2 and does not work with 2.1.1. Other pyplot functions do not exhibit this behavior. E.g., plt.plot(np.zeros((2,1)),np.zeros((2,1))) works fine.

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    API: argument checkingValidation of acceptable argument valuesAPI: consistencyConsistency of the matplotlib API, including naming, behavior, defaults, …status: closed as inactiveIssues closed by the "Stale" Github Action. Please comment on any you think should still be open.status: inactiveMarked by the “Stale” Github Action

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