title: Rotate theta=0 on matplotlib polar plot
body: <p>I have the following example code:</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  import random
  
  data_theta = range(10,171,10)
  
  data_theta_rad = []
  for i in data_theta:
      data_theta_rad.append(float(i)*np.pi/180.0)
  
  data_r = random.sample(range(70, 90), 17)
  
  print data_theta
  print data_r
  
  ax = plt.subplot(111, polar=True)
  ax.plot(data_theta_rad, data_r, color='r', linewidth=3)
  ax.set_rmax(95)
  # ax.set_rmin(70.0)
  ax.grid(True)
  
  ax.set_title("Example", va='bottom')
  plt.show()
  </code></pre>
  
  <p>...which produces something like this:
  <img src="https://i.stack.imgur.com/HlnI7.png" alt="enter image description here"></p>
  
  <p>...but I would like to set theta=0 to the 'West'. So something like:</p>
  
  <p><img src="https://i.stack.imgur.com/hmzbU.png" alt="enter image description here"></p>
  
  <p>Any ideas how to do this with matplotlib (I made the pic below in powerpoint) ?</p>