title: Polar heatmaps in python
body: <p>I want to plot a paraboloid  f(r) = r**2 as a 2D polar heatmap. The output I expect is <a href="https://i.stack.imgur.com/4qWaG.png" rel="noreferrer"><img src="https://i.stack.imgur.com/4qWaG.png" alt="enter image description here"></a></p>
  
  <p>The code that I have written is </p>
  
  <pre><code>from pylab import*
  from mpl_toolkits.mplot3d import Axes3D
  ax = Axes3D(figure())
  rad=linspace(0,5,100)
  azm=linspace(0,2*pi,100)
  r,th=meshgrid(rad,azm)
  z=(r**2.0)/4.0
  subplot(projection="polar")
  pcolormesh(r,th, z)
  show()
  </code></pre>
  
  <p>But this program returns the following image. <a href="https://i.stack.imgur.com/sHkqF.png" rel="noreferrer"><img src="https://i.stack.imgur.com/sHkqF.png" alt="enter image description here"></a></p>
  
  <p>Can someone help? Thank you in advance.</p>