Index: lib/matplotlib/lines.py
===================================================================
RCS file: /cvsroot/matplotlib/matplotlib/lib/matplotlib/lines.py,v
retrieving revision 1.36
diff -r1.36 lines.py
15c15,16
<      compress, zeros, concatenate, cumsum
---
>      compress, zeros, concatenate, cumsum, \
>      matrixmultiply
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> import math
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>                   'a':1,
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>         'a'  : '_draw_arrow_head',
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>                 
>     def _draw_arrow_head(self, renderer, gc, xt, yt):
>         offset = renderer.points_to_pixels(self._markersize)
>         rgbFace = self._get_rgb_face()
>         hoffset = offset / 2.0
>         poly = array([
>             [0.0, 0.0],
>             [-offset, -hoffset],
>             [-offset, hoffset],
>         ])
>         npts = len(xt) - 1
>         if npts < 1:
>             return
>         points = zip(xt, yt)
>         if self._newstyle:
>             points = self._transform.seq_xy_tups(points)
>         for i in range(npts):
>             (x1, y1), (x2, y2) = points[i], points[i+1]
>             dx = x2 - x1
>             dy = y2 - y1
>             ang = math.atan2(dy, dx)
>             cx = math.cos(ang)
>             sx = math.sin(ang)
>             M = array([[cx, sx], [-sx, cx]])
>             npoly = matrixmultiply(poly, M) + [x2, y2]
>             verts = [tuple(t) for t in npoly]
>             renderer.draw_polygon(gc, rgbFace, verts)