Re: [Matplotlib-users] contour coordinates

[Eli B. <eb...@gm...>]

Many thanks to Jeff and to Patric !
I will try to work along the line suggested by Jeff.
Patric, please send me your code.
I hope to learn from it.

Thanks again,
Eli



On Tue, Jan 27, 2009 at 7:09 PM, Patrick Marsh <pat...@gm...>wrote:

> On Tue, Jan 27, 2009 at 5:33 PM, Jeff Whitaker <js...@fa...> wrote:
> > 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
> >
> > --
> > Jeffrey S. Whitaker         Phone  : (303)497-6313
> > Meteorologist               FAX    : (303)497-6449
> > NOAA/OAR/PSD  R/PSD1        Email  : Jef...@no...
> > 325 Broadway                Office : Skaggs Research Cntr 1D-113
> > Boulder, CO, USA 80303-3328 Web    : http://tinyurl.com/5telg
> >
> >
> >
> >
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>
> I'm not sure if this is entirely what you (Eli) are looking for, but I
> have code that will contour model data on a map and then extract the
> lat,lon pairs of all the vertices.  If this is what you are looking
> for, I'm happy to share what I've done.
>
> -Patrick
>
> --
> Patrick Marsh
> Graduate Research Assistant
> School of Meteorology
> University of Oklahoma
> http://www.patricktmarsh.com
>