James Boyle wrote: > 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.
I think that something close to my example should do the job. It sounds like your difficulty is with the colorbar; but colorbar gives quite a bit of control via the kwargs, and you can also drop back from colorbar.Colorbar (which the pylab colorbar command uses) to colorbar.ColorbarBase, using the colorbar.Colorbar code as an example. I don't think you should need to use an intermediate ScalarMappable subclass, although this may be a perfectly good approach. Eric > > 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
