Re: [Matplotlib-users] Clipping Contours

[Damon M. <dam...@gm...>]

On Tue, Oct 16, 2012 at 8:04 AM, T J <tj...@gm...> wrote:
> I'm interested in clipping the result of plt.contour (and
> plt.contourf) to a patch.  However, QuadContourSet does not have a
> set_clip_path() method.  Is there a way to do this?
>
> Here is an example plot that I have generated.
>
>    http://imgur.com/pybIf
>
> For the curious, it plots contours of a function on the 2-simplex.
> The way I've gone about computing this is, unfortunately, convoluted.
> I generate a regular grid in 2D and treat each point as a projection
> of a 3D probability vector into 2D.  Then, I invert the projection so
> that I have "distributions" and then compute the Z value for each
> point.  The contours are then calculated, but now, I need to clip
> everything outside the triangle, as only points within the triangle
> correspond to actual distributions.
>
> Is there a more direct way to calculate contours on a restricted set?
>
> Thanks.

The contour functions support masked regions. I think that might be
what you're looking for. Since the region you want to mask is a
triangle, maybe even use a masked triangulated contour plot? Here's
the call signature:
http://matplotlib.org/api/pyplot_api.html#matplotlib.pyplot.tricontour

Does that help?

-- 
Damon McDougall
http://www.damon-is-a-geek.com
B2.39
Mathematics Institute
University of Warwick
Coventry
West Midlands
CV4 7AL
United Kingdom