title: How to change the axis dimension from pixel to length in matplotlib? is there any code in general?
body: <p>Since the complete simulation is to big to post it right here only the code to plot the spectrum is given (I think this is enough)</p>
  
  <pre><code>d = i.sum(axis=2)
  pylab.figure(figsize=(15,15))
  pylab = imshow(d)
  plt.axis('tight')
  pylab.show()
  </code></pre>
  
  <p>This spectrum is given in pixel. But I would like to have this in the units of length. I will hope you may give me some advices. </p>