Merge pull request #12492 from anntzer/radar

QuLogic · web-flow · commit 2d2d3e52bcd9 · 2018-10-12T19:08:36.000-04:00
Simplify radar_chart example.
diff --git a/examples/specialty_plots/radar_chart.py b/examples/specialty_plots/radar_chart.py
@@ -13,13 +13,16 @@
 
 .. [1] http://en.wikipedia.org/wiki/Radar_chart
 """
+
 import numpy as np
 
 import matplotlib.pyplot as plt
+from matplotlib.patches import Circle, RegularPolygon
 from matplotlib.path import Path
-from matplotlib.spines import Spine
 from matplotlib.projections.polar import PolarAxes
 from matplotlib.projections import register_projection
+from matplotlib.spines import Spine
+from matplotlib.transforms import Affine2D
 
 
 def radar_factory(num_vars, frame='circle'):
@@ -38,26 +41,11 @@ def radar_factory(num_vars, frame='circle'):
     # calculate evenly-spaced axis angles
     theta = np.linspace(0, 2*np.pi, num_vars, endpoint=False)
 
-    def draw_poly_patch(self):
-        # rotate theta such that the first axis is at the top
-        verts = unit_poly_verts(theta + np.pi / 2)
-        return plt.Polygon(verts, closed=True, edgecolor='k')
-
-    def draw_circle_patch(self):
-        # unit circle centered on (0.5, 0.5)
-        return plt.Circle((0.5, 0.5), 0.5)
-
-    patch_dict = {'polygon': draw_poly_patch, 'circle': draw_circle_patch}
-    if frame not in patch_dict:
-        raise ValueError('unknown value for `frame`: %s' % frame)
-
     class RadarAxes(PolarAxes):
 
         name = 'radar'
         # use 1 line segment to connect specified points
         RESOLUTION = 1
-        # define draw_frame method
-        draw_patch = patch_dict[frame]
 
         def __init__(self, *args, **kwargs):
             super().__init__(*args, **kwargs)
@@ -86,39 +74,37 @@ def set_varlabels(self, labels):
             self.set_thetagrids(np.degrees(theta), labels)
 
         def _gen_axes_patch(self):
-            return self.draw_patch()
+            # The Axes patch must be centered at (0.5, 0.5) and of radius 0.5
+            # in axes coordinates.
+            if frame == 'circle':
+                return Circle((0.5, 0.5), 0.5)
+            elif frame == 'polygon':
+                return RegularPolygon((0.5, 0.5), num_vars,
+                                      radius=.5, edgecolor="k")
+            else:
+                raise ValueError("unknown value for 'frame': %s" % frame)
 
         def _gen_axes_spines(self):
             if frame == 'circle':
                 return super()._gen_axes_spines()
-            # The following is a hack to get the spines (i.e. the axes frame)
-            # to draw correctly for a polygon frame.
-
-            # spine_type must be 'left', 'right', 'top', 'bottom', or `circle`.
-            spine_type = 'circle'
-            verts = unit_poly_verts(theta + np.pi / 2)
-            # close off polygon by repeating first vertex
-            verts.append(verts[0])
-            path = Path(verts)
-
-            spine = Spine(self, spine_type, path)
-            spine.set_transform(self.transAxes)
-            return {'polar': spine}
+            elif frame == 'polygon':
+                # spine_type must be 'left'/'right'/'top'/'bottom'/'circle'.
+                spine = Spine(axes=self,
+                              spine_type='circle',
+                              path=Path.unit_regular_polygon(num_vars))
+                # unit_regular_polygon gives a polygon of radius 1 centered at
+                # (0, 0) but we want a polygon of radius 0.5 centered at (0.5,
+                # 0.5) in axes coordinates.
+                spine.set_transform(Affine2D().scale(.5).translate(.5, .5)
+                                    + self.transAxes)
+                return {'polar': spine}
+            else:
+                raise ValueError("unknown value for 'frame': %s" % frame)
 
     register_projection(RadarAxes)
     return theta
 
 
-def unit_poly_verts(theta):
-    """Return vertices of polygon for subplot axes.
-
-    This polygon is circumscribed by a unit circle centered at (0.5, 0.5)
-    """
-    x0, y0, r = [0.5] * 3
-    verts = [(r*np.cos(t) + x0, r*np.sin(t) + y0) for t in theta]
-    return verts
-
-
 def example_data():
     # The following data is from the Denver Aerosol Sources and Health study.
     # See doi:10.1016/j.atmosenv.2008.12.017
