Use splines to render circles in scatter plots.

svn path=/trunk/matplotlib/; revision=5641

CHANGELOG

@@ -1,3 +1,5 @@
+2008-06-23 Use splines to render circles in scatter plots - MGD
+
 ===============================================================
 2008-06-22 Released 0.98.1 at revision 5637
 

lib/matplotlib/axes.py

@@ -4561,22 +4561,23 @@ def scatter(self, x, y, s=20, c='b', marker='o', cmap=None, norm=None,
             The marker can also be a tuple (*numsides*, *style*,
             *angle*), which will create a custom, regular symbol.
 
-            *numsides*:
-              the number of sides
+              *numsides*:
+                the number of sides
 
-            *style*:
-              the style of the regular symbol:
+              *style*:
+                the style of the regular symbol:
 
-              =====   ==================
-              Value   Description
-              =====   ==================
-              0       a regular polygon
-              1       a star-like symbol
-              2       an asterisk
-              =====   ==================
+                =====   ==================
+                Value   Description
+                =====   =========================================
+                0       a regular polygon
+                1       a star-like symbol
+                2       an asterisk
+                3       a circle (numsides and angle is ignored)
+                =====   =========================================
 
-            *angle*:
-              the angle of rotation of the symbol
+              *angle*:
+                the angle of rotation of the symbol
 
             Finally, *marker* can be (*verts*, 0): *verts* is a
             sequence of (*x*, *y*) vertices for a custom scatter
@@ -4640,7 +4641,7 @@ def scatter(self, x, y, s=20, c='b', marker='o', cmap=None, norm=None,
 
         syms =  { # a dict from symbol to (numsides, angle)
             's' : (4,math.pi/4.0,0),   # square
-            'o' : (20,0,0),            # circle
+            'o' : (20,3,0),            # circle
             '^' : (3,0,0),             # triangle up
             '>' : (3,math.pi/2.0,0),   # triangle right
             'v' : (3,math.pi,0),       # triangle down
@@ -4748,9 +4749,16 @@ def scatter(self, x, y, s=20, c='b', marker='o', cmap=None, norm=None,
                     offsets = zip(x,y),
                     transOffset = self.transData,
                     )
+            elif symstyle==3:
+                collection = mcoll.CircleCollection(
+                    scales,
+                    facecolors = colors,
+                    edgecolors = edgecolors,
+                    linewidths = linewidths,
+                    offsets = zip(x,y),
+                    transOffset = self.transData,
+                    )
         else:
-            # MGDTODO: This has dpi problems
-            # rescale verts
             rescale = np.sqrt(max(verts[:,0]**2+verts[:,1]**2))
             verts /= rescale
 

lib/matplotlib/collections.py

@@ -805,6 +805,32 @@ def get_color(self):
         return self._edgecolors
     get_colors = get_color  # for compatibility with old versions
 
+class CircleCollection(Collection):
+    """
+    A collection of circles, drawn using splines.
+    """
+    def __init__(self, sizes):
+        """
+        *sizes*
+            Gives the area of the circle in points^2
+
+        %(Collection)s
+        """
+        Collection.__init__(self,**kwargs)
+        self._sizes = sizes
+        self.set_transform(transforms.IdentityTransform())
+        self._paths = [mpath.Path.unit_circle()]
+
+    def draw(self, renderer):
+        # sizes is the area of the circle circumscribing the polygon
+        # in points^2
+        self._transforms = [
+            transforms.Affine2D().scale(
+                (np.sqrt(x) * renderer.dpi / 72.0) / np.sqrt(np.pi))
+            for x in self._sizes]
+        return Collection.draw(self, renderer)
+
+
 class PatchCollection(Collection):
     """
     A generic collection of patches.
@@ -870,6 +896,6 @@ def get_paths(self):
 
 artist.kwdocd['Collection'] = patchstr = artist.kwdoc(Collection)
 for k in ('QuadMesh', 'PolyCollection', 'BrokenBarHCollection', 'RegularPolyCollection',
-          'StarPolygonCollection'):
+          'StarPolygonCollection', 'PatchCollection', 'CircleCollection'):
     artist.kwdocd[k] = patchstr
 artist.kwdocd['LineCollection'] = artist.kwdoc(LineCollection)