Wrong offset when using math mode and subscripts in Matplotlib and OSX

Question

I have some plots where I would like to use subindices in some labels but whenever I use math mode all the labels appear shifted. Can I set some offset for all my labels? Is there anything I'm missing for using math mode?

This is the plot without math mode in the labels:

And this is what it looks like with math mode (notice the ticks):

For reference, here is my full code (I got the stacked code from ):

import numpy as NP
import matplotlib.patches as mpatches
import matplotlib.pyplot as plt
import matplotlib.cm as cm
data = '''0    0    0    0    0    0    0    0
0    0    0    0    0    0    0.015    0.015
0    0    0    0    0    0    0    0
0    0    0    0    0.04    0.04    0    0
0    0    0    0    0.03    0.01    0.19    0.14
0    0    0.772    0    0.07    0.01    0.12    0.11
0    0.879    0    0    0    0.07    0    0.085
0.056    0    0    0    0    0    0    0
'''.splitlines()
data = tuple(reversed([NP.array([float(j) for j in i.split('    ')]) for i in data]))
colors = cm.rainbow(NP.linspace(0, 1, 8))
axes = plt.figure().add_subplot(111)
axes.set_xticklabels([r'$m_%d$'%i for i in ([i+1 for i in range(8)])])
plt.stackplot(NP.arange(8)+1,
          data, 
          colors=colors)
plt.xlim(1,8)
plt.ylabel("Error")  
plt.legend([mpatches.Patch(color=i) for i in colors], 
           [r'$m_%d$'%i for i in ([i+1 for i in range(8)])])
plt.show()

Update: The problem resided on the backend used for interactive display

Following the hints provided in the comments I tried writing to a file and the labels appear properly. The problem seem to be on the MacOSX backend.

Python 2.7.9 (default, Dec 11 2014, 02:36:08) [GCC 4.2.1 Compatible Apple LLVM 5.1 (clang-503.0.40)] on darwin
matplotlib.version 1.4.3
matplotlib.get_backend() MacOSX

What backend are you using? This may be a bug in the OSX backend. If you have to png does it look ok? — tacaswell
– tacaswell, Commented Jul 29, 2015 at 4:03
Tested your code in Ubuntu 15.04, Python 2.7.9, matplotlib 1.4.2, and with Agg backend. Labels of the xaxis and in legend all appears ok. BTW, if you want your labels to look like normal text, you can do r'$\mathregular{m_%d}$'. — Jean-Sébastien
– Jean-Sébastien, Commented Jul 29, 2015 at 6:39
@ThePredator well, plt.rc('font', family='serif') won't help you much with the subscripts... — Jean-Sébastien
– Jean-Sébastien, Commented Jul 29, 2015 at 12:57
The problem seems to be on the MacOSX backend when displaying to screen, should I report a bug to Matplotlib? — Josep Valls
– Josep Valls, Commented Jul 29, 2015 at 16:42

Josep Valls · Accepted Answer · 2015-07-29 16:52:06Z

0

There seems to be a bug on the MacOSX backend for Matplotlib. In order to solve it I had to switch the backend. I tried several from the FAQ (http://matplotlib.org/faq/usage_faq.html#what-is-a-backend) and I got best results using WXAgg. TkAgg was very sluggish and WX does NOT support math mode. If anyone is interested, the code to be added before importing pyplot is:

import matplotlib
matplotlib.use('WXAgg')

This are the results (all look slightly different):

WXAgg

TkAgg

WX

answered Jul 29, 2015 at 16:52

Josep Valls

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