Re: [Matplotlib-users] Trouble with legend and axis scaling

[Sterling S. <sm...@fu...>]

Frix,

It may be useful to post the version and backend you are using to the list.

import matplotlib
print matplotlib.__version__
print matplotlib.get_backend()

Also, if you can format the code as a simple self-contained example, that would help others confirm what you are seeing.

-Sterling

On Mar 26, 2013, at 12:01PM, Hackstein wrote:

> Hello everyone,
>  
> I have two issues with my current projects:
>  
> 1)  I automatically generate plots of several data sets in a for-loop, all of which have the same shape of x and y values, but some of which have two of those data (i.e. graphs) sets per figure, others have only one.
> I create the legend by
>  
> plt.legend(bbox_to_anchor=(0., 1.02, 1., 0.102), loc=3, mode='expand', numpoints=1, borderaxespad=0.)
>  
> which works perfectly if I plot two data sets (and therefore two labels) in a figure, but sometimes (not always) causes an error, if only one data set is plotted in a figure.
> The legend is this
>  
> print ax.get_legend_handles_labels()
> ([<matplotlib.lines.Line2D object at 0x24b9550>], ['i_s'])
>  
> and the error is
>  
> File "/usr/lib64/python2.6/site-packages/matplotlib/offsetbox.py", line 76, in _get_packed_offsets
>     sep = (total - sum(w_list)) / (len(w_list) - 1.)
> FloatingPointError: divide by zero encountered in double_scalars
>  
> which I broke down to a problem with the" mode='expand'" parameter. It seems it cannot expand when the number of labels is 1. Strangely, however, that seems not always to be the case, since some of the plots with only one data set and one legend entry work without problems, but some raise an error.
>  
> 2) Another problem occurs with the y-axis tick labels. Even if the y-values are quite ordinary (in the order of 10) the labels get scientific notation when the y-range is small (order 0.1). I don't know why that is and it only occurs then. When the y-range is larger (order of 1), the ticks get plain numbers. I tried to work around that with the following code, which did not
> work:
>  
> plt.figure("i_only", figsize=(14.40, 9.00), dpi=100) plt.plot(np.asarray(mod_mjd_list_i), np.asarray(x_i), 'r-', label = 'i_s') ax = plt.gca() formy = plt.ScalarFormatter() formy.set_powerlimits((-5, 5))
> formy.set_scientific(False)
> ax.yaxis.set_major_formatter(formy)
>  
> Any ideas what I can do?
>  
> Thanks,
> frix
>  
>  
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