matplotlib
diff --git a/‎lib/matplotlib/collections.py
Lines changed: 7 additions & 1 deletion b/‎lib/matplotlib/collections.py
Lines changed: 7 additions & 1 deletion
diff --git a/‎lib/matplotlib/tests/baseline_images/test_collections/regularpolycollection_rotate.png
-31.1 KB b/‎lib/matplotlib/tests/baseline_images/test_collections/regularpolycollection_rotate.png
-31.1 KB
diff --git a/‎lib/matplotlib/tests/baseline_images/test_collections/regularpolycollection_scale.png
3.8 KB b/‎lib/matplotlib/tests/baseline_images/test_collections/regularpolycollection_scale.png
3.8 KB
diff --git a/‎lib/matplotlib/tests/test_collections.py
Lines changed: 30 additions & 0 deletions b/‎lib/matplotlib/tests/test_collections.py
Lines changed: 30 additions & 0 deletions
@@ -725,6 +725,8 @@ class _CollectionWithSizes(Collection):
     """
     Base class for collections that have an array of sizes.
     """
+    _factor = 1.0
+
     def get_sizes(self):
         """
         Returns the sizes of the elements in the collection.  The
@@ -756,7 +758,7 @@ def set_sizes(self, sizes, dpi=72.0):
         else:
             self._sizes = np.asarray(sizes)
             self._transforms = np.zeros((len(self._sizes), 3, 3))
-            scale = np.sqrt(self._sizes) * dpi / 72.0
+            scale = np.sqrt(self._sizes) * dpi / 72.0 * self._factor
             self._transforms[:, 0, 0] = scale
             self._transforms[:, 1, 1] = scale
             self._transforms[:, 2, 2] = 1.0
@@ -894,6 +896,8 @@ class RegularPolyCollection(_CollectionWithSizes):
     """Draw a collection of regular polygons with *numsides*."""
     _path_generator = mpath.Path.unit_regular_polygon
 
+    _factor = 1.0 / np.sqrt(np.pi)
+
     @docstring.dedent_interpd
     def __init__(self,
                  numsides,
@@ -1401,6 +1405,8 @@ class CircleCollection(_CollectionWithSizes):
     """
     A collection of circles, drawn using splines.
     """
+    _factor = 1.0 / np.sqrt(np.pi)
+
     @docstring.dedent_interpd
     def __init__(self, sizes, **kwargs):
         """
 
@@ -529,6 +529,36 @@ def test_regularpolycollection_rotate():
     ax.autoscale_view()
 
 
+@image_comparison(baseline_images=['regularpolycollection_scale'],
+                  extensions=['png'], remove_text=True)
+def test_regularpolycollection_scale():
+    # See issue #3860
+
+    class SquareCollection(mcollections.RegularPolyCollection):
+        def __init__(self, **kwargs):
+            super(SquareCollection, self).__init__(4, rotation=np.pi/4., **kwargs)
+
+        def get_transform(self):
+            """Return transform scaling circle areas to data space."""
+            ax = self.axes
+
+            pts2pixels = 72.0 / ax.figure.dpi
+
+            scale_x = pts2pixels * ax.bbox.width / ax.viewLim.width
+            scale_y = pts2pixels * ax.bbox.height / ax.viewLim.height
+            return mtransforms.Affine2D().scale(scale_x, scale_y)
+
+    fig, ax = plt.subplots()
+
+    xy = [(0, 0)]
+    # Unit square has a half-diagonal of `1 / sqrt(2)`, so `pi * r**2` equals...
+    circle_areas = [np.pi / 2]
+    squares = SquareCollection(sizes=circle_areas, offsets=xy,
+                               transOffset=ax.transData)
+    ax.add_collection(squares, autolim=True)
+    ax.axis([-1, 1, -1, 1])
+
+
 if __name__ == '__main__':
     import nose
     nose.runmodule
328F
(argv=['-s', '--with-doctest'], exit=False)