Learn what to expect in the new updates
It is clear that polar plots need to be able to gracefully handle negative r values (not by clipping or reflection).
One obvious application that we should support is bB plots (see
https://github.com/matplotlib/matplotlib/issues/1730#issuecomment-40815837),
but this seems more generally useful (for example growth rate as a
function of angle). The assumption in the current code (as I
understand it) is that the center of the graph is r==0, however it
would be good to be able to set the center to be at any r (with any
value less than the off set clipped).