Description

astrofrog

opened on Jun 8, 2011

Issue body actions

The following code works:

import matplotlib as mpl
mpl.use('Agg')
import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
ax.contourf([[0.,1.], [1.,0.]], levels=[0.5, 1.0, 2.0])
fig.savefig('contourf.png')

but if I try and specify a single level, the code crashes:

import matplotlib as mpl
mpl.use('Agg')
import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
ax.contourf([[0.,1.], [1.,0.]], levels=[0.5])
fig.savefig('contourf.png')

The exception is:

Traceback (most recent call last):
  File "test.py", line 7, in <module>
    ax.contourf([[0.,1.], [1.,0.]], levels=[0.5])
  File "/Users/tom/Library/Python/2.6/site-packages/matplotlib/axes.py", line 7403, in contourf
    return mcontour.QuadContourSet(self, *args, **kwargs)
  File "/Users/tom/Library/Python/2.6/site-packages/matplotlib/contour.py", line 1103, in __init__
    ContourSet.__init__(self, ax, *args, **kwargs)
  File "/Users/tom/Library/Python/2.6/site-packages/matplotlib/contour.py", line 719, in __init__
    self.allsegs, self.allkinds = self._get_allsegs_and_allkinds()
  File "/Users/tom/Library/Python/2.6/site-packages/matplotlib/contour.py", line 1136, in _get_allsegs_and_allkinds
    lowers, uppers = self._get_lowers_and_uppers()
  File "/Users/tom/Library/Python/2.6/site-packages/matplotlib/contour.py", line 820, in _get_lowers_and_uppers
    if self.zmin == lowers[0]:
IndexError: index out of bounds

Activity

1. efiring commented on Jun 8, 2011

   

   efiring

   on Jun 8, 2011

   Member

   More actions

   On 06/08/2011 11:18 AM, astrofrog wrote:

   The following code works:

    import matplotlib as mpl
    mpl.use('Agg')
    import matplotlib.pyplot as plt
   
    fig = plt.figure()
    ax = fig.add_subplot(1, 1, 1)
    ax.contourf([[0.,1.], [1.,0.]], levels=[0.5, 1.0, 2.0])
    fig.savefig('contourf.png')
   

   but if I try and specify a single level, the code crashes:

    import matplotlib as mpl
    mpl.use('Agg')
    import matplotlib.pyplot as plt
   
    fig = plt.figure()
    ax = fig.add_subplot(1, 1, 1)
    ax.contourf([[0.,1.], [1.,0.]], levels=[0.5])
    fig.savefig('contourf.png')
   

   contourf contours between levels, so there is not much it can do with
   a single level. The error (an invalid input) could be trapped at an
   early stage. That sort of input validation is done somewhat erratically
   in mpl. Personally, I don't want to see us try to anticipate every
   possible input error and clutter the code with validation, but some
   types of error are worth trapping.

   Eric

   The exception is:

    Traceback (most recent call last):
      File "test.py", line 7, in<module>
        ax.contourf([[0.,1.], [1.,0.]], levels=[0.5])
      File "/Users/tom/Library/Python/2.6/site-packages/matplotlib/axes.py", line 7403, in contourf
        return mcontour.QuadContourSet(self, *args, **kwargs)
      File "/Users/tom/Library/Python/2.6/site-packages/matplotlib/contour.py", line 1103, in __init__
        ContourSet.__init__(self, ax, *args, **kwargs)
      File "/Users/tom/Library/Python/2.6/site-packages/matplotlib/contour.py", line 719, in __init__
        self.allsegs, self.allkinds = self._get_allsegs_and_allkinds()
      File "/Users/tom/Library/Python/2.6/site-packages/matplotlib/contour.py", line 1136, in _get_allsegs_and_allkinds
        lowers, uppers = self._get_lowers_and_uppers()
      File "/Users/tom/Library/Python/2.6/site-packages/matplotlib/contour.py", line 820, in _get_lowers_and_uppers
        if self.zmin == lowers[0]:
    IndexError: index out of bounds
   
2. astrofrog commented on Jun 8, 2011

   

   astrofrog

   on Jun 8, 2011

   ContributorAuthor

   More actions

   Ok, that makes sense. One possibility would be that if the length of the levels iterable is 1, one could append +inf as the second value (since that is probably the expected behavior if people try and specify a single value). Just a thought, but feel free to close the ticket without any changes.
3. efiring commented on Jun 16, 2011

   

   efiring

   on Jun 16, 2011

   Member

   More actions

   Closed with 58c4713. It turns out that a check for 2 or more levels for contourf was already being made, but it was missing the case where the levels were specified via a kwarg. I slight rearrangement fixed that.
4. efiring

   closed this as completedon Jun 16, 2011

Issue actions