Eric, Thanks for the quick reply. I should have looked more closely at the examples for the contourf solution. As I indicated, my problem is a bit beyond contours. I have routines that fill polygons ( finite element mesh) using a specified color map. The ability to fill areas with the proper color is easy - getting the corresponding color bar has been the more interesting part. It is going to take some time to look over your suggestion to see how I could implement it in my application. Presently I sub-class scalarMappable, and set the appropriate values and pass this to colorbar(). However, I have not been able to figure out how to do this for non-uniform intervals. This is a long winded way of saying that getting pcolor and matshow to work may or may not solve my specific problem.
Thanks again, --Jim On Apr 18, 2007, at 1:52 AM, Eric Firing wrote: > James Boyle wrote: >> I wish to make a color filled plot with the colors defined for >> discrete, non-uniform intervals. Something like: >> 0.0 -0.001 0.001-0.05 0.05-0.2 0.2-0.4 0.4-0.8 >> 0.8-1.0 >> red blue green magenta >> yellow cyan >> with the colorbar labeled appropriately. >> I have seen discussions and solutions for discrete colors but not >> for non-uniform intervals + discrete. >> The last post I saw regarding this type of issue was august 2005 >> - and a solution was not resolved at that time. >> However, Eric has done a huge amount of work in the intervening >> time and a smarter person than myself might have a solution now. >> Note that I do not wish just to make contours - although that >> would be good - but to have a general mapping code that joins >> allows the color rmapping to be passed to colorbar. >> maybe some sub-class of scalarMappable that could work. > > This is very easy for contourf, and is illustrated in the second > figure made by examples/contourf_demo.py. For your case above, it > would be something like > > levs = [0, 0.001, 0.05, 0.2, 0.4, 0.8, 1] > colors = ['r', 'b', 'g', 'm', 'y', 'c'] > contourf(z, levs, colors=colors) > colorbar() > > Unfortunately, although it *should* be just as easy for imshow or > pcolor, it is not at present; it can be done, probably in several > ways, but not in such a transparent way. Attached is a quick > attempt at something that might be close to what you need. The > right way to do this is to make some changes and additions to > colors.py and colorbar.py; I might get to that in a few days, or, > more likely, it might be a few weeks. > > Eric > >> Thanks for any help. >> --Jim > import pylab as P > import numpy > from matplotlib import colors > > class BoundaryNorm(colors.Normalize): > def __init__(self, boundaries): > self.vmin = boundaries[0] > self.vmax = boundaries[-1] > self.boundaries = boundaries > self.N = len(self.boundaries) > > def __call__(self, x, clip=False): > x = numpy.asarray(x) > ret = numpy.zeros(x.shape, dtype=numpy.int) > for i, b in enumerate(self.boundaries): > ret[numpy.greater_equal(x, b)] = i > ret[numpy.less(x, self.vmin)] = -1 > ret = numpy.ma.asarray(ret / float(self.N-1)) > return ret > > bounds = [0, 0.1, 0.5, 1] > cm = colors.ListedColormap(['r', 'g', 'b']) > > z = (numpy.arange(5)[:,None] * numpy.arange(8)[None,:]).astype > (numpy.float) > z = z / z.max() > > P.pcolor(z, cmap=cm, norm=BoundaryNorm(bounds)) > P.colorbar(boundaries=bounds) > P.show() ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
