[Matplotlib-users] Trouble with legend and axis scaling

[Hackstein <new...@gm...>]

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