Small improvements related to radar_chart example.

A small block at the end of polar.py is described as not strictly
necessary, but is in fact used by the radar_chart example.  Perhaps a
unittest would be better, but for now, just note that this should not be
changed without manual checking.

RESOLUTION is unused; remove it.

Author: anntzer

examples/specialty_plots/radar_chart.py

@@ -55,8 +55,6 @@ def transform_path_non_affine(self, path):
     class RadarAxes(PolarAxes):
 
         name = 'radar'
-        # use 1 line segment to connect specified points
-        RESOLUTION = 1
         PolarTransform = RadarTransform
 
         def __init__(self, *args, **kwargs):

lib/matplotlib/projections/polar.py

@@ -1444,9 +1444,12 @@ def drag_pan(self, button, key, x, y):
             self.set_rmax(p.rmax / scale)
 
 
-# to keep things all self contained, we can put aliases to the Polar classes
+# To keep things all self-contained, we can put aliases to the Polar classes
 # defined above. This isn't strictly necessary, but it makes some of the
-# code more readable (and provides a backwards compatible Polar API)
+# code more readable, and provides a backwards compatible Polar API. In
+# particular, this is used by the :doc:`/gallery/specialty_plots/radar_chart`
+# example to override PolarTransform on a PolarAxes subclass, so make sure that
+# that example is unaffected before changing this.
 PolarAxes.PolarTransform = PolarTransform
 PolarAxes.PolarAffine = PolarAffine
 PolarAxes.InvertedPolarTransform = InvertedPolarTransform