Issue with hist plotting

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.

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

···

On 08/14/2010 04:47 AM, Daπid wrote:

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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2010/8/14 Eric Firing <efiring@...202...>:

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 :slight_smile:

Friedrich

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.

···

On Sat, Aug 14, 2010 at 10:19 PM, Eric Firing <efiring@...202...> 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.

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

···

On 08/22/2010 04:51 AM, Daπid wrote:

On Sat, Aug 14, 2010 at 10:19 PM, Eric Firing<efiring@...202...> wrote:

Thank you again,

David.