Re: [Matplotlib-users] selecting part of a contour to plot

[Jonathan S. <js...@cf...>]

Thanks to Benjamin Root and Jae-Joon Lee for their responses.

The solution that I had come up with in the mean time is similar to
Jae-Joon's suggestion.  I did:

c = contour(z,level,colors='k')
xy = c.collections[0].get_paths()[0].vertices  # produces (N,2) array of points
plot(xy[:,0],xy[:,1],'w')

c.collections[0].get_paths() returns a list of Path objects.  These have
the attribute vertices which contains the values used to draw the
contour.  Jae-Joon's method is a bit more straightforward than mine,
though it's nice to know where those contour paths are stored.

Jon

On Tue, 2010-06-22 at 22:40 -0400, Jae-Joon Lee wrote:
> contour creates list of LineCollection objects (per each level I
> suppose) which is stored in "collections" attribute. For example,
> 
> cntr = contour(A, levels)
> 
> then
> 
> cntr.collections[i] is a LineCollection objects that is associated
> with levels[i].
> 
> And you can change colors of each line in the LineCollection object
> with set_edgecolors method.
> 
> So, assuming that there is two contour lines for the first level.
> 
> cntr.collections[0].set_edgecolors(["none", "r"])
> 
> will change the color of the first contour to "none" (i.e., not drawn)
> and the second one to red.
> 
> But you need to figure out which one is the one you want.
> 
> IHTH,
> 
> -JJ
> 
> 
> On Tue, Jun 22, 2010 at 2:46 PM, Jonathan Slavin
> <js...@cf...> wrote:
> > To all:
> >
> > I'm making a plot with an image and a contour on it.  I use only one
> > level in the call to contour, but it results in two distinct contours,
> > an inner closed one and an outer open one.  I want to plot only the
> > outer piece.  How might I go about that?  I've been looking at the
> > properties of the ContourSet object returned by the call to contour but
> > can't find anything useful yet.  Is there an attribute of ContourSet
> > objects that contains the (x,y) values for the contour?  Is there some
> > way to see that a ContourSet object has separate pieces?
> >
> > Any help would be appreciated.
> >
> > Thanks,
> > Jon
> >
> >
> > ------------------------------------------------------------------------------
> > ThinkGeek and WIRED's GeekDad team up for the Ultimate
> > GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the
> > lucky parental unit.  See the prize list and enter to win:
> > http://p.sf.net/sfu/thinkgeek-promo
> > _______________________________________________
> > Matplotlib-users mailing list
> > Mat...@li...
> > https://lists.sourceforge.net/lists/listinfo/matplotlib-users
> >
-- 
______________________________________________________________
Jonathan D. Slavin              Harvard-Smithsonian CfA
js...@cf...         60 Garden Street, MS 83
phone: (617) 496-7981           Cambridge, MA 02138-1516
 cell: (781) 363-0035           USA
______________________________________________________________