title: Python: AttributeError in plotting a 3d surface
body: <p>I am trying to plot a 3d surface by having coordinates of x,y and values as w1. I have checked the dimensions by shape(), they match. but I receive the error that "AttributeError: 'module' object has no attribute 'plot_surface'"</p>
  
  <p>Code:</p>
  
  <pre><code>import numpy as np
  import math
  import matplotlib.pyplot as plt
  from mpl_toolkits.mplot3d import Axes3D
  </code></pre>
  
  <p>.
  .
  .</p>
  
  <pre><code>x = np.arange(xmin, xmax+dx, dx)
  z = np.arange(zmin, zmax+dz, dz)
  X, Z = np.meshgrid(x, z)
  #print X.shape, Z.shape, w1.shape
  plt.plot_surface(X, Z, w1)
  plt.show()
  </code></pre>