[Matplotlib-users] matplotlib compilation and running issues

[Jeff Blackburne]

Hi Jason,

$DISPLAY should normally look like HOSTNAME:X where HOSTNAME is your local
machine's hostname and X is some number. That's assuming you have a
graphical display running. Matplotlib is trying to start up one of its
interactive backends, but cannot because your $DISPLAY is blank. You can
fix this by setting $DISPLAY to its proper value, or by switching backends
to a non-interactive backend like 'agg', which will let you save figures to
disk.

I can't help you with the former, except to say that if you are connecting
to a remote machine using ssh, you can try forwarding your local display to
the remote machine using ssh -X.

To do the latter, insert these 2 lines before your code:
import matplotlib as mpl
mpl.use('agg')

-Jeff


On Thu, Sep 17, 2015 at 11:04 AM, Jason Snyder <jmssnyder at ucdavis.edu>
wrote:

> To who it may concern,
>
> I installed matplotlib on my computer and tried to run a program with the
> code below:
>
> import numpy as np
> import matplotlib.pyplot as plt
>
>
> x = np.linspace(0, 10)
> line, = plt.plot(x, np.sin(x), '--', linewidth=2)
>
> When I ran the program I could the below error output:
>
> [vrsops at am-linux-212 cpcharts]$ python line_demo_dash_control.py
> Traceback (most recent call last):
>   File "line_demo_dash_control.py", line 12, in <module>
>     line, = plt.plot(x, np.sin(x), '--', linewidth=2)
>   File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py", line
> 3092, in plot
>     ax = gca()
>   File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py", line
> 828, in gca
>     ax =  gcf().gca(**kwargs)
>   File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py", line
> 462, in gcf
>     return figure()
>   File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py", line
> 435, in figure
>     **kwargs)
>   File
> "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_qt4agg.py",
> line 47, in new_figure_manager
>     return new_figure_manager_given_figure(num, thisFig)
>   File
> "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_qt4agg.py",
> line 54, in new_figure_manager_given_figure
>     canvas = FigureCanvasQTAgg(figure)
>   File
> "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_qt4agg.py",
> line 72, in __init__
>     FigureCanvasQT.__init__(self, figure)
>   File
> "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_qt4.py",
> line 68, in __init__
>     _create_qApp()
>   File
> "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_qt5.py",
> line 138, in _create_qApp
>     raise RuntimeError('Invalid DISPLAY variable')
> RuntimeError: Invalid DISPLAY variable
>
> What is causing these errors and how do I resolve this issue?  Also echo
> $DISPLAY is blank.
>
> Thank you for your time.
>
> -Jason
>
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>
>
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