Hi all, just a little question : how matplotlib computes contours? Is it based on an internal library? Is it possible to access it from outside? Thanks
Le vendredi 30 janvier 2009 à 10:22 -0500, Eli Brosh a écrit : > Hello again, > 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 > <patrickmars...@gmail.com> wrote: > On Tue, Jan 27, 2009 at 7:16 PM, Eli Brosh <ebro...@gmail.com> > wrote: > > 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 > > > > Here is a template that can be used. I use this for > meteorological > 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 > <patrickmars...@gmail.com> > > wrote: > >> > >> On Tue, Jan 27, 2009 at 5:33 PM, Jeff Whitaker > <jsw...@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.whita...@noaa.gov > >> > 325 Broadway Office : Skaggs Research Cntr > 1D-113 > >> > Boulder, CO, USA 80303-3328 Web : > http://tinyurl.com/5telg > >> > > >> > > >> > > >> > > >> > > > ------------------------------------------------------------------------------ > >> > 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 > >> > > >> > >> 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 > > > ------------------------------------------------------------------------------ > 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 -- Lionel Roubeyrie chargé d'études LIMAIR - La Surveillance de l'Air en Limousin http://www.limair.asso.fr ------------------------------------------------------------------------------ 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
