I finally found the command I was looking for. It is the to_polygons().

Here is what worked :

# make a LineCollection of contours

col=contour(X,Y,Z,LevelsNumber).collections

for i in np.arange(0,LevelsNumber,1):

polygoni=col[i].get_paths()[0].to_polygons()[0]

print polygoni

All the vertices in each collections are extracted to the "polygoni".

Thanks again to Jeff and Patrick !

By the way, I found out that I do not actually need this procedure to achieve may goal

which was to make a contour plot in ternary coordinates.

Eli

On Tue, Jan 27, 2009 at 11:08 PM, Patrick Marsh <patrickmarshwx@gmail.com> wrote:

On Tue, Jan 27, 2009 at 7:16 PM, Eli Brosh <ebrosh1@gmail.com> wrote:Here is a template that can be used. I use this for meteorological

> 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

models, but should work with any gridded file.

import numpy as np

from mpl_toolkits.basemap import Basemap

f = (some gridded file)

X = np.array(grab longitudes from f)

Y = np.array(grab latitudes from f)

field = np.array(grab field to be contoured from f)

map = Basemap(make a Basemap call here)

level = np.arange(minval, maxval, interval)

col = map.contour(X, Y, field, level).collections

for vertex in col[i].get_paths(): # GET THE PATHS FOR THE EACH

CONTOUR BY LOOPING THROUGH CONTOURS

for vertex in xy.vertices: # ITERATE OVER THE PATH OBJECTS

x, y = map(vertex[0],vertex[1],inverse=True) # vertex[0]

and now 'x' is the longitude of the vertex and vertex[1] and now 'y'

is the latitude of the vertex

Let me know how this works.

-Patrick

--

>

> On Tue, Jan 27, 2009 at 7:09 PM, Patrick Marsh <patrickmarshwx@gmail.com>

> wrote:

>>

>> On Tue, Jan 27, 2009 at 5:33 PM, Jeff Whitaker <jswhit@fastmail.fm> 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 : Jeffrey.S.Whitaker@noaa.gov

>> > 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

>

>

Patrick Marsh

Graduate Research Assistant

School of Meteorology

University of Oklahoma

http://www.patricktmarsh.com