matplotlib-users Mailing List for matplotlib

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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YAxis:
The documentation (http://matplotlib.sourceforge.net/api/axis_api.html) says: 

"Set the ticks position (left, right, both, default or none) 'both' sets the ticks to appear on both positions, but does not change the tick labels. 'default' resets the tick positions to the default: ticks on both positions, labels at left. 'none' can be used if you don't want any ticks. 'none' and 'both' affect only the ticks, not the labels."

To test this: 

f=figure()
plot()
gca().xaxis.set_ticks_position('none')
gca().yaxis.set_ticks_position('none')
f.show()

The y labels, on my 1.0.0 distribution, disappear, because of this line of code:

        elif position == 'none':
            self.set_tick_params(which='both', right=False, labelright=False,
                                 left=False, labelleft=False)
the work-around is to execute that line without turning off the labels.  

------------------------------------
show()

This may be an ipython problem, when running it with the -pylab option, the show method now has a Tk.mainloop(), which blocks of course. The work-around it to call the Figure.show() method instead, as above.

--Toby Burnett
University of Washington

Hi all,

First: I noticed in the changelog to 1.0 that a lot of work has gone 
into splines.  Thanks!

In particular, I notice commit message "splines and ticks: implement 
smart bounds" from 20 Dec 2009 (commit 
58d31c10eef8648cd0fb81d5c0f0bcd0c05fe9a1 in astraw's github repository, 
labeled as git-svn-id: 
https://matplotlib.svn.sourceforge.net/svnroot/matplotlib/trunk/matplotlib@8048 
f61c4167-ca0d-0410-bb4a-bb21726e55ed).

What are "smart bounds"?  It looks desirable to do, but it defaults to 
off, I think.

Thanks,

Jason

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.

On 8/12/10 10:57 PM, Aman Thakral wrote:
> I'm fairly sure its just a contour plot with different color mappings
> for the lines and the fill.

Yeah, I think so but I can't get it right. So if anybody knows what to
grep/search for in revisions or which revision it was in that would be
much appreciated.

Best
Simon

>> 
> 
> Agreed. The only thing I can think of is that the second figure is
> reusing the first. You can try calling plt.figure() at the beginning
> of the functions to create a new figure, or call plt.figure() in
> between the calls to CreateMemberStatCategoryFigure() and
> CreateMemberStatFigure(). I can't be sure since you didn't include the
> code that actually calls these functions.
> 
> Ryan
> 
> 
> -- 
> Ryan May
> Graduate Research Assistant
> School of Meteorology
> University of Oklahoma
> 
> -

Ryan,

Thanks.  Indeed I did provide the code that actually calls these functions and the functions show all plotting-related lines.  Yes, I did not provide the single line call that calls the function that calls the two plotting functions, nor did I provide the call which starts the Python program. And I did not provide runnable code. Everyone's attention was on what code I did or did not provide. It was all there.  Naively I thought by code inspection by experts who read this mailing list they could quickly spot my flaw.

And a flaw it turned out to be.

I took your suggestion to put a plt.figure() call at the beginning of each function that generates a plot and the problem disappeared.  Now calling each plotting function sequentially within the same instance of a Python program the second plot does not get scrambled.  This is good as it now provides the automation I was hoping for.

I've now also found http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.figure and http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.close which look to be important.  I was not aware of the need for these functions before.  Oversight on my part. Using them now.

I'm now off doing more productive things.  thanks for the pointer!!