title: How to limit the range of the x-axis with imshow()?
body: <p>I have the following data</p>
  
  <pre><code>1.105   0.919   0.842   0.715   0.704   0.752   0.827   1.049   0.584   
  0.998   0.931   0.816   0.787   0.803   0.856   0.782   0.872   0.710   
  1.268   1.189   1.036   0.984   0.847   0.948   1.083   0.864   0.792
  </code></pre>
  
  <p>that I plot with <code>imshow()</code> </p>
  
  <p>The result looks like this:
  <img src="https://i.stack.imgur.com/TOmOS.png" alt="enter image description here"></p>
  
  <p>Here is my code:</p>
  
  <pre><code>from numpy import*
  import matplotlib.cm as cm
  import matplotlib.mlab as mlab
  import matplotlib.pyplot as plt
  from mpl_toolkits.axes_grid1 import make_axes_locatable
  
  shape=(3,9)
  velocity=zeros(shape)
  
  
  fig = plt.figure(figsize=(16, 12), dpi=100)
  ax1 = fig.add_subplot(111,aspect='equal')
  #   ax1.set_yticks([int(100*j) for j in range(0,4)])
  ax1.set_yticks([int(j) for j in range(0,4)])
  ax1.set_xticks([int(j) for j in range(-4,5)])
  for label in ax1.get_xticklabels() + ax1.get_yticklabels():
      label.set_fontsize(15)
  for tick in ax1.get_xticklines() + ax1.get_yticklines():
      tick.set_markeredgewidth(2)
      tick.set_markersize(6)
  ax1.set_aspect("equal") 
  velocity=loadtxt("fieldvelocitybot-300-100-100_400.dat")
  
  im = plt.imshow(velocity, cmap=cm.jet, interpolation='nearest',origin='lower',vmin=0,vmax=1.7, extent=[-4.50,4.50,0.,3.00])
  
  divider = make_axes_locatable(ax1)
  cax = divider.append_axes("right", size="2.5%", pad=0.3)
  cb=plt.colorbar(im,cax=cax)
  cb.set_label('Speed [$m/s$]')
  plt.savefig("speed_400.png")
  plt.close(fig)
  </code></pre>
  
  <p>My problem is: How to show just the results from -4 to 4? Intuitively I thought of changing <code>extent=[-4.00,4.00,0.,3.00]</code>, but the axis is then just shifted. The result is like this:
  <img src="https://i.stack.imgur.com/g448U.png" alt="enter image description here"></p>