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I would like to create a histogram and save it to a file without showing it on the screen. The piece of code I have now is showing the figure by default and I cannot find any way to suppress showing the figure. I have tried pyplot.hist(nrs) as well, with the same problem. 

import math, time, matplotlib.pyplot as plt, pylab; 
import numpy as np; 

nrs = [1.0, 2.0, 1.0, 3.0, 4.0]
freq,bins = np.histogram(nrs)
fig = plt.figure(figsize=(5,4), dpi=100); 
freq = np.append(freq, [0.0])
graph = fig.add_subplot(111);
x = graph.bar(bins, freq)

fig.savefig( "test.png")
Monique Hendriks
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  • I can't reproduce this behaviour(matplotlib 1.3.1). What version are you using? – igavriil Mar 18 '15 at 15:01
  • are you sure you don't have `plt.show()` or `fig.show()` anywhere in your code? – Srivatsan Mar 18 '15 at 15:08
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    Just save this as a .py script and run it with `python script.py`. This should work. The only way you could be getting a figure without calling `plt.show()` is with interactive mode in IPython. – rth Mar 18 '15 at 15:14
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    You want to use one of the headless backends (ex `Agg`). See http://stackoverflow.com/questions/2801882/generating-a-png-with-matplotlib-when-display-is-undefined/3054314#3054314 for an example (slightly different issue there, but same solution). – tacaswell Mar 18 '15 at 16:29
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    You might be using an interactive client (IPython). `plt.ioff()` would turn *autoploting* off. – Imanol Luengo Mar 18 '15 at 20:02

1 Answers1

7

Thank you tcasewell, adding 

import matplotlib
# Force matplotlib to not use any Xwindows backend.
matplotlib.use('Agg')

Before importing pyplot solved the problem.

Monique Hendriks
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