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. > > ------------------------------------------------------------------------------ > This SF.net email is sponsored by > > Make an app they can't live without > Enter the BlackBerry Developer Challenge > http://p.sf.net/sfu/RIM-dev2dev > _______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/matplotlib-users ------------------------------------------------------------------------------ This SF.net email is sponsored by Make an app they can't live without Enter the BlackBerry Developer Challenge http://p.sf.net/sfu/RIM-dev2dev _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
