title: Setting theta-ticks in matplotlib polar plots
body: <p>My question is related to the following:
  <a href="https://stackoverflow.com/questions/20317481/scatter-polar-plot-in-matlab">Scatter polar plot in matlab</a></p>
  
  <p>I tried looking online but couldn't find any with this axis; instead of the polar plot going 0 to 360 degrees how can I do -180 to 180 instead?</p>