title: Set radial axis on Matplotlib polar plots
body: <p>I'm plotting an azimuth-elevation curve on a polar plot where the elevation is the radial component. By default, Matplotlib plots the radial value from 0 in the center to 90 on the perimeter. I want to reverse that so 90 degrees is at the center. I tried setting the limits with a call to ax.set_ylim(90,0) but this results in a LinAlgError exception being thrown. ax is the axes object obtained from a call to add_axes.</p>
  
  <p>Can this be done and, if so, what must I do?</p>
  
  <p>Edit: Here is what I'm using now. The basic plotting code was taken from one of the Matplotlib examples</p>
  
  <pre><code># radar green, solid grid lines
  rc('grid', color='#316931', linewidth=1, linestyle='-')
  rc('xtick', labelsize=10)
  rc('ytick', labelsize=10)
  
  # force square figure and square axes looks better for polar, IMO
  width, height = matplotlib.rcParams['figure.figsize']
  size = min(width, height)
  # make a square figure
  fig = figure(figsize=(size, size))
  ax = fig.add_axes([0.1, 0.1, 0.8, 0.8], projection='polar', axisbg='#d5de9c')
  
  # Adjust radius so it goes 90 at the center to 0 at the perimeter (doesn't work)
  #ax.set_ylim(90, 0)
  
  # Rotate plot so 0 degrees is due north, 180 is due south
  
  ax.set_theta_zero_location("N")
  
  obs.date = datetime.datetime.utcnow()
  az,el = azel_calc(obs, ephem.Sun())
  ax.plot(az, el, color='#ee8d18', lw=3)
  obs.date = datetime.datetime.utcnow()
  az,el = azel_calc(obs, ephem.Moon())
  ax.plot(az, el, color='#bf7033', lw=3)
  
  ax.set_rmax(90.)
  grid(True)
  
  ax.set_title("Solar Az-El Plot", fontsize=10)
  show()
  </code></pre>
  
  <p>The plot that results from this is</p>
  
  <p><img src="https://i.stack.imgur.com/1FXRw.png" alt="enter image description here"></p>