On Fri, Jan 23, 2009 at 2:06 PM, Michael Hearne <mhea...@usgs.gov> wrote:
> I have discovered, from the mailing list, the easy way to draw a circle
> in linear space:
> ...snip
> cx = 700
> cy = 700
> r = 1000
>
> xmin = cx - r
> xmax = cx + r
> ymin = cy - r
> ymax = cy + r
>
> cir = Circle( (cx,cx), radius=r,facecolor='w',edgecolor='b')
> a = gca()
> a.add_patch(cir)
>
> axis([xmin,xmax,ymin,ymax])
> axis('equal')
>
> How can I plot a circle in log space?
The problem is that your circle has negative vertices since cx-r<0 and
cy-r<0. When this happens, mpl is transforming the vertices with log
coordinates and getting nans, as it should. The problem is that these
nan vertices are getting passed to the agg backend, and when the
vertex type is curve4, as it is for a circle, agg gets stuck in an
infinite recursion in the spline code. I suspect this is because the
recursion expects the comparison operator on the vertices to be well
behaved, but it is not in the presence of nans. The function in
question is agg_curve.cpp curve4_div::recursive_bezier. There is a
"maximum recursion limit" in that function, but for some reason I
don't understand, it is not breaking out of the function.
I committed a simple "fix" to the branch and the trunk to simply drop
any patch where any of the vertices are nans
if not np.isnan(tpath.vertices).any():
renderer.draw_path(gc, tpath, affine, rgbFace)
We might be able to do better than this -- is there a well defined way
to deal with patches where any of the transformed vertices are nans?
For simple polygons (no splines vertices), we could plot the polygon
with all the nan containing vertices removed, though in some cases
this could be a strange object -- this appears to be what was
happening by default with CirclePolygon with negative vertices but I
think this was mostly fortuitous that agg dealt with the nans
gracefully in this case. But for patches containing curve vertices,
this seems like a bad idea, since simply dropping vertices from a
spline curve is not defined.
I'm including below some sample code that shows the bug on Agg
JDH
import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
import matplotlib.patches as patches
cx = 700
cy = 700
r = 1000
fig = plt.figure()
ax = fig.add_subplot(111)
#cir = patches.CirclePolygon( (cx,cy), radius=r,facecolor='w',edgecolor='b')
cir = patches.Circle( (cx,cy), radius=r,facecolor='w',edgecolor='b')
ax.add_patch(cir)
ax.set_yscale('log')
fig.savefig('test')
plt.show()
------------------------------------------------------------------------------
This SF.net email is sponsored by:
SourcForge Community
SourceForge wants to tell your story.
http://p.sf.net/sfu/sf-spreadtheword
_______________________________________________
Matplotlib-users mailing list
Matplotlib-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/matplotlib-users
