Re: [Matplotlib-users] contour coordinates

[Jeff W. <js...@fa...>]

Eli Brosh wrote:
> Hello,
> I am trying to extract the coordinates of contour lines.
> I tried the following:
>
> cs = *contour*(Z)
> for lev, col in zip(cs.levels, cs.collections):
>      s = col._segments
>
> that I found in a previous post (title "contouring", by Jose 
> Gómez-Dans-2 <http://www.nabble.com/user/UserProfile.jtp?user=30071> 
> Nov 30, 2007; 07:47am ) .
>
> I hoped that s will be a list of numpy arrays, each containing the 
> (x,y) vertices
> defining a contour line at level lev.
> However, I got an error message:
> AttributeError: 'LineCollection' object has no attribute '_segments'
>
>
> How is it possible to get coordinates of the contours, similar to the 
> MATLAB command
>  [C,H] = *CONTOUR*(...)
> where the result in C is the coordinates of the contours.
>
> A similar question appeared in a post "contour data" (by Albert Swart 
> <http://www.nabble.com/user/UserProfile.jtp?user=382945> May 17, 2006; 
> 09:42am) but I could not understand the answer.
> Is it possible to get more specific directions with a simple example ?
>
>
> Thanks
> Eli
Eli:  Calling get_paths() on each line collection in CS.collections will 
return a list of Path objects.  From the Path objects, you can get a Nx2 
array of vertices from the "vertices" attribute.  There are no examples 
that I know of, but if you get it to do what you want to do, it would be 
great if you could contribute an example.  As you noted, this question 
has come up several times before.

-Jeff

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