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davidleejy opened this issue Aug 23, 2018 · 3 comments
Closed

Wrong Error Message #11919

davidleejy opened this issue Aug 23, 2018 · 3 comments
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API: argument checking
Milestone
v3.2.0

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@davidleejy
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davidleejy commented Aug 23, 2018 •
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Bug report

Affects: commit 7b5ff33 (master, 23 Aug 2018)

An attempt to plot a single point at coords (2,3) with RGB color (120,130,140) throws an error message remarking about argument shapes mismatching. Message should be about RGB values outside range 0 to 1.

Code for reproduction

ax.scatter(np.array([2]), np.array([3]), c=np.array([[120,130,140]]))
ValueError: c of shape (1, 3) not acceptable as a color sequence for x with size 1, y with size 1

This is ok:

ax.scatter(np.array([2]), np.array([3]), c=np.array([[120,130,140]]) / 255.0 )

Actual outcome

See above.

Expected outcome

Suggestion: error message could be about RGB values outside of 0 to 1 range.

Trace

  File "/home/d/code/matplotlib/lib/matplotlib/axes/_axes.py", line 4223, in scatter
    .format(nc=n_elem, xs=x.size, ys=y.size)
ValueError: 'c' argument has 3 elements, which is not acceptable for use with 'x' with size 1, 'y' with size 1.

python 2 gives slightly different trace:

/home/d/.conda/envs/py2_dp/lib/python2.7/site-packages/matplotlib-2.2.2-py2.7-linux-x86_64.egg/matplotlib/axes/_axes.pyc in scatter(self, x, y, s, c, marker, cmap, norm, vmin, vmax, alpha, linewidths, verts, edgecolors, **kwargs)
   4277                 raise ValueError("c of shape {} not acceptable as a color "
   4278                                  "sequence for x with size {}, y with size {}"
-> 4279                                  .format(c.shape, x.size, y.size))
   4280         else:
   4281             colors = None  # use cmap, norm after collection is created

ValueError: c of shape (1, 3) not acceptable as a color sequence for x with size 1, y with size 1

Matplotlib version

  • Operating system: Ubuntu 16.04
  • Matplotlib version: commit 7b5ff33 (master, 23 Aug 2018)
  • Matplotlib backend (print(matplotlib.get_backend())): <object object at 0x7f8885d87190>
  • Python version: 3.5.5
  • Jupyter version (if applicable): none
  • Other libraries: numpy

How I installed matplotlib:

  1. Create new conda env with python 3.5.5
  2. git clone matplotlib master
  3. pip install -e /path/to/cloned-repo
@afvincent
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@davidleejy Thank you for the extensive ticket :).

FTR, the difference between Python 2 and 3 is “simply” related to #11383.

@afvincent afvincent added this to the v3.1 milestone Aug 23, 2018
@davidleejy davidleejy mentioned this issue Aug 24, 2018
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@wangjiawen2013 wangjiawen2013 mentioned this issue Nov 30, 2018
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@tacaswell tacaswell modified the milestones: v3.1.0, v3.2.0 Mar 18, 2019
@anntzer
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anntzer commented Jun 24, 2019

For the better or the worst (mostly the worst, IMO, but see discussion in #12735), the error message is also correct, because c could be colormapped data (and x/y could indeed have been badly sized): something like

scatter(np.array([[0, 1, 2]]), np.array([[0, 1, 2]]), c=np.array([[120, 130, 140]]))

works.

Note that as of master, the exception is

Traceback (most recent call last):
  <elided>
ValueError: RGBA values should be within 0-1 range

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  <elided>
ValueError: 'c' argument has 3 elements, which is inconsistent with 'x' and 'y' with size 1.

which seems not too bad, so I'm suggesting to close this.

efiring added a commit to efiring/matplotlib that referenced this issue Jul 1, 2019
@efiring
Improve error reporting for scatter c as invalid RGBA.
c77bfe0 
Closes matplotlib#11919.
@efiring efiring mentioned this issue Jul 1, 2019
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@efiring
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efiring commented Jul 5, 2019

Closing as suggested by @anntzer

@efiring efiring closed this as completed Jul 5, 2019
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Improve error reporting for scatter c as invalid RGBA. efiring/matplotlib
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@efiring @tacaswell @anntzer @davidleejy @afvincent