matplotlib-users

[Matplotlib-users] Issue with hist plotting

[Daπid <dav...@gm...>]

Hello.

I have had an issue trying to plot an histogram with Matplotlib. The line is:

plt.hist([SNIa.angles, SNIbc.angles, SNII.angles], 11, range=[-pi, pi],
         normed=True,histtype='stepfilled',color=['g', 'r',
'b'],alpha=[1, 0.6, 1])

But the error is raised when I try to save the image. For completness,
the  whole program is here:
http://nopaste.voric.com/paste.php?f=8zl9i4

If I call hist as stated above, I get the following error report:

Traceback (most recent call last):
  File "C:\Documents and
Settings\David\Escritorio\Python\IAYC\Supernovae\final\Deprecated\supernovae_bug.py",
line 35, in <module>
    plt.savefig('angular_merged_1bis.png')
  File "C:\Python25\Lib\site-packages\matplotlib\pyplot.py", line 363,
in savefig
    return fig.savefig(*args, **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\figure.py", line
1084, in savefig
    self.canvas.print_figure(*args, **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\backend_bases.py",
line 1886, in print_figure
    **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\backends\backend_agg.py",
line 438, in print_png
    FigureCanvasAgg.draw(self)
  File "C:\Python25\Lib\site-packages\matplotlib\backends\backend_agg.py",
line 394, in draw
    self.figure.draw(self.renderer)
  File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\figure.py", line 798, in draw
    func(*args)
  File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\axes.py", line 1934, in draw
    a.draw(renderer)
  File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\patches.py", line 366, in draw
    r, g, b, a = colors.colorConverter.to_rgba(self._facecolor, self._alpha)
  File "C:\Python25\Lib\site-packages\matplotlib\colors.py", line 353,
in to_rgba
    raise ValueError('to_rgba: Invalid rgba arg "%s"\n%s' % (str(arg), exc))
ValueError: to_rgba: Invalid rgba arg "[ 0.   0.5  0.   1. ]"
alpha must be in range 0-1



If I delete the color declaring, I get instead:

Traceback (most recent call last):
  File "C:\Documents and
Settings\David\Escritorio\Python\IAYC\Supernovae\final\Deprecated\supernovae_bug.py",
line 35, in <module>
    plt.savefig('angular_merged_1bis.png')
  File "C:\Python25\Lib\site-packages\matplotlib\pyplot.py", line 363,
in savefig
    return fig.savefig(*args, **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\figure.py", line
1084, in savefig
    self.canvas.print_figure(*args, **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\backend_bases.py",
line 1886, in print_figure
    **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\backends\backend_agg.py",
line 438, in print_png
    FigureCanvasAgg.draw(self)
  File "C:\Python25\Lib\site-packages\matplotlib\backends\backend_agg.py",
line 394, in draw
    self.figure.draw(self.renderer)
  File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\figure.py", line 798, in draw
    func(*args)
  File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\axes.py", line 1934, in draw
    a.draw(renderer)
  File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python25\Lib\site-packages\matplotlib\patches.py", line 383, in draw
    renderer.draw_path(gc, tpath, affine, rgbFace)
  File "C:\Python25\Lib\site-packages\matplotlib\backends\backend_agg.py",
line 117, in draw_path
    self._renderer.draw_path(gc, path, transform, rgbFace)
TypeError: float() argument must be a string or a number

And works fine without alpha statement. Any change in the other
arguments does not make any difference on the behaviour.

If I run it from the IDLE, once I get an error, I continue getting it
even if the problematic part is fixed, until I restart the program. I
am running Matplotlib 1.0.0 y Python 2.5 sobre WXP.

I haven't find any reference to this in the documentation, so it seems
to be a bug.



Regards,

David.

Re: [Matplotlib-users] Issue with hist plotting

[Eric F. <ef...@ha...>]

On 08/14/2010 04:47 AM, Daπid wrote:
> Hello.
>
> I have had an issue trying to plot an histogram with Matplotlib. The line is:
>
> plt.hist([SNIa.angles, SNIbc.angles, SNII.angles], 11, range=[-pi, pi],
>           normed=True,histtype='stepfilled',color=['g', 'r',
> 'b'],alpha=[1, 0.6, 1])

The problem is that the "alpha" kwarg can never be other than a scalar 
in mpl at present, as far as I know.  The error message from to_rgba was 
intended to be informative, but in this case it is misleading.

If you want different alpha values for your different bars, you will 
have to use a list of rgba values for your color kwarg, and leave out 
the alpha kwarg.  You can construct the list like this (untested):

from matplotlib.colors import colorConverter

colors = [colorConverter.to_rgba(c, a) for c, a in zip(['g', 'r', 'b'], 
[1, 0.6, 1]]

Eric

>
> But the error is raised when I try to save the image. For completness,
> the  whole program is here:
> http://nopaste.voric.com/paste.php?f=8zl9i4
>
> If I call hist as stated above, I get the following error report:
>
> Traceback (most recent call last):
>    File "C:\Documents and
> Settings\David\Escritorio\Python\IAYC\Supernovae\final\Deprecated\supernovae_bug.py",
> line 35, in<module>
>      plt.savefig('angular_merged_1bis.png')
>    File "C:\Python25\Lib\site-packages\matplotlib\pyplot.py", line 363,
> in savefig
>      return fig.savefig(*args, **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\figure.py", line
> 1084, in savefig
>      self.canvas.print_figure(*args, **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\backend_bases.py",
> line 1886, in print_figure
>      **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\backends\backend_agg.py",
> line 438, in print_png
>      FigureCanvasAgg.draw(self)
>    File "C:\Python25\Lib\site-packages\matplotlib\backends\backend_agg.py",
> line 394, in draw
>      self.figure.draw(self.renderer)
>    File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
> in draw_wrapper
>      draw(artist, renderer, *args, **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\figure.py", line 798, in draw
>      func(*args)
>    File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
> in draw_wrapper
>      draw(artist, renderer, *args, **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\axes.py", line 1934, in draw
>      a.draw(renderer)
>    File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
> in draw_wrapper
>      draw(artist, renderer, *args, **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\patches.py", line 366, in draw
>      r, g, b, a = colors.colorConverter.to_rgba(self._facecolor, self._alpha)
>    File "C:\Python25\Lib\site-packages\matplotlib\colors.py", line 353,
> in to_rgba
>      raise ValueError('to_rgba: Invalid rgba arg "%s"\n%s' % (str(arg), exc))
> ValueError: to_rgba: Invalid rgba arg "[ 0.   0.5  0.   1. ]"
> alpha must be in range 0-1
>
>
>
> If I delete the color declaring, I get instead:
>
> Traceback (most recent call last):
>    File "C:\Documents and
> Settings\David\Escritorio\Python\IAYC\Supernovae\final\Deprecated\supernovae_bug.py",
> line 35, in<module>
>      plt.savefig('angular_merged_1bis.png')
>    File "C:\Python25\Lib\site-packages\matplotlib\pyplot.py", line 363,
> in savefig
>      return fig.savefig(*args, **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\figure.py", line
> 1084, in savefig
>      self.canvas.print_figure(*args, **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\backend_bases.py",
> line 1886, in print_figure
>      **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\backends\backend_agg.py",
> line 438, in print_png
>      FigureCanvasAgg.draw(self)
>    File "C:\Python25\Lib\site-packages\matplotlib\backends\backend_agg.py",
> line 394, in draw
>      self.figure.draw(self.renderer)
>    File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
> in draw_wrapper
>      draw(artist, renderer, *args, **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\figure.py", line 798, in draw
>      func(*args)
>    File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
> in draw_wrapper
>      draw(artist, renderer, *args, **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\axes.py", line 1934, in draw
>      a.draw(renderer)
>    File "C:\Python25\Lib\site-packages\matplotlib\artist.py", line 55,
> in draw_wrapper
>      draw(artist, renderer, *args, **kwargs)
>    File "C:\Python25\Lib\site-packages\matplotlib\patches.py", line 383, in draw
>      renderer.draw_path(gc, tpath, affine, rgbFace)
>    File "C:\Python25\Lib\site-packages\matplotlib\backends\backend_agg.py",
> line 117, in draw_path
>      self._renderer.draw_path(gc, path, transform, rgbFace)
> TypeError: float() argument must be a string or a number
>
> And works fine without alpha statement. Any change in the other
> arguments does not make any difference on the behaviour.
>
> If I run it from the IDLE, once I get an error, I continue getting it
> even if the problematic part is fixed, until I restart the program. I
> am running Matplotlib 1.0.0 y Python 2.5 sobre WXP.
>
> I haven't find any reference to this in the documentation, so it seems
> to be a bug.
>
>
>
> Regards,
>
> David.
>
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Re: [Matplotlib-users] Issue with hist plotting

[Friedrich R. <fri...@gm...>]

2010/8/14 Eric Firing <ef...@ha...>:
> colors = [colorConverter.to_rgba(c, a) for c, a in zip(['g', 'r', 'b'],

If it is this (I didn't dig into the program) it will be fixed soon I hope :-)

Friedrich

Re: [Matplotlib-users] Issue with hist plotting

[Daπid <dav...@gm...>]

On Sat, Aug 14, 2010 at 10:19 PM, Eric Firing <ef...@ha...> wrote:
> The problem is that the "alpha" kwarg can never be other than a scalar
> in mpl at present, as far as I know.  The error message from to_rgba was
> intended to be informative, but in this case it is misleading.

Thanks for your response. I was following the logic for colors, which
does accept lists.

Anyway, the error message is diferent if I set the color or not, which
is not logical.

By the way, do you have any clue on the persistence of the problem
until the IDLE is restarted? I mean, even with the code fixed, the
error is still raised until IDLE is reopened.


Thank you again,

David.

Re: [Matplotlib-users] Issue with hist plotting

[Eric F. <ef...@ha...>]

On 08/22/2010 04:51 AM, Daπid wrote:
> On Sat, Aug 14, 2010 at 10:19 PM, Eric Firing<ef...@ha...>  wrote:
>> The problem is that the "alpha" kwarg can never be other than a scalar
>> in mpl at present, as far as I know.  The error message from to_rgba was
>> intended to be informative, but in this case it is misleading.
>
> Thanks for your response. I was following the logic for colors, which
> does accept lists.

That was a reasonable thing to do, but unfortunately, for historical 
reasons, there are inconsistencies and ambiguities associates with the 
alpha kwarg in mpl.

>
> Anyway, the error message is diferent if I set the color or not, which
> is not logical.

Granted.  This is one of many situations in which the error message is 
not very informative.  We don't have a consistent policy for validating 
kwargs, so invalid values can filter down into the depths of the code 
before they trigger an exception.

>
> By the way, do you have any clue on the persistence of the problem
> until the IDLE is restarted? I mean, even with the code fixed, the
> error is still raised until IDLE is reopened.
>

If you are fixing code that is in a module that has been imported, IDLE 
may be using the old code, not the new.  This is inherent in 
python--importing a module that has already been imported does not rerun 
the code in that module, or change any existing objects.  There are ways 
of getting around this, at least with respect to function and class 
definitions, but usually it is easier, surer, and cleaner to restart the 
python interpreter so that everything is clearly using the new code.

Eric

>
> Thank you again,
>
> David.