title: Plotting nxn Matrix visualized as (n-1)x(n-1) Matrix with pyplot.pcolor
body: <p>I am creating a n times n Matrix and plot it with <code>plt.pcolor()</code> in two different ways.</p>
  
  <ol>
  <li><code>plt.pcolor(X,Y,C)</code>: Since the axis are not arbitrary but have a certain range, say from 0 to 1, i want to specify the axis in order to get the plot right. But when I specify the axis, the matrix gets truncated to a 4x4 matrix (left subplot). I do not want to have that.</li>
  <li><code>plt.pcolor(C)</code>: If i do not define the axis, the matrix is displayed as expected, but of course the axis tick labels are enumerated and do not lie in the range which I want to have (right subplot).
  <img src="https://i.stack.imgur.com/Xm9WM.png" alt="enter image description here"></li>
  </ol>
  
  <p>What i want to have is a mixture of both subplots. I want the matrix visualized as in the second subplot, but the axis tick labels as in the first subplot.
  I have a workaround in mind by just using the second option and overwriting the axis tick labels afterwards, but I think there must be a more natural solution to this. </p>
  
  <p>Here is the code snipped i wrote to produce the figure:</p>
  
  <pre><code>import numpy
  from matplotlib import pyplot as plt
  
  # graphic parameters
  fig = plt.figure()
  plt.ion()
  plt.set_cmap('bwr')
  
  # Some data
  a = numpy.linspace(0, 1, 5)
  b = numpy.linspace(0, 1, 5)
  A, B = numpy.meshgrid(a, b)
  
  # plt.pcolor(X,Y,C) --&gt; plots 4x4 matrix
  ax = fig.add_subplot(1, 2, 1)
  plt.pcolor(a, b, A-B, vmin=-1, vmax=1)
  plt.colorbar(orientation='horizontal')
  
  # plt.pcolor(C) --&gt; plots 5x5 matrix 
  ax = fig.add_subplot(1, 2, 2)
  plt.pcolor(A-B, vmin=-1, vmax=1)
  plt.colorbar(orientation='horizontal')
  </code></pre>