On 10/26/2010 04:50 AM, Maarten Sneep wrote: > Hi, > > I did solve my own question. For posterity, and perhaps for a more > elegant solution, I post my solution here. > > On Tue, 2010-10-26 at 10:56 +0200, Maarten Sneep wrote: > >> I have an image with cloud pressures, 1000 at the surface, 200 at the >> top of the atmosphere. I'd like to reverse the axis, i.e. 1000 at the >> bottom of the scale, 200 at the top. How should I approach this? > > Instead of using a figure.colorbar() call, I instantiate ColorbarBase > directly. I needed an axes object anyway to use a single colorbar fro a > two-subplot figure. The ColorbarBase gets the reversed colormap compared > to the image. > > fig = plt.figure() > norm=Normalize(vmin=200.0, vmax=1000.0, clip=False) > cmap = cm.jet > cmap.set_bad(color=(0.75,0.75, 0.75)) > cmap.set_over(color=(1.0, 1.0, 1.0)) > cmap.set_under(color=(0.5, 0.5, 0.5)) > cmap_bar = cm.jet_r > # note that under and over are reversed. > cmap_bar.set_bad(color=(0.75,0.75, 0.75)) > cmap_bar.set_under(color=(1.0, 1.0, 1.0)) > cmap_bar.set_over(color=(0.5, 0.5, 0.5)) > > # make subplots > ax1 = fig.add_subplot(211) > ax1.imshow(cp1, origin='lower', cmap=cmap, > interpolation='nearest', aspect='auto', norm=norm) > ax2 = fig.add_subplot(212) > ax2.imshow(cp2, origin='lower', cmap=cmap, > interpolation='nearest', aspect='auto', norm=norm) > > # make room for colorbar > plt.subplots_adjust(left=0.07, hspace=0.25, right=0.825) > cbar_ax = plt.axes([0.875, 0.1, 0.025, 0.8]) > tickvals = [200, 400, 600, 800, 1000] > cbar = ColorbarBase(cbar_ax, cmap=cmap_bar, > ticks=tickvals, extend='both', norm=norm) > # I use latex formatting, original is more interesting. > labels = ['%d' % v for v in tickvals] > cbar.ax.set_yticklabels(lblslabels[::-1]) > > Dirty: yes, and it only works because of the equidistant labels. A more > elegant solution is appreciated.
Illustrated using ipython -pylab: z = rand(10, 12) im = imshow(z) cbar = colorbar(im, extend='both') cbar.ax.invert_yaxis() # This is the key method. draw() > >> Related: I have set colors for under- and over-values. I'd like to >> display a small patch of these colors at either end of the scale. The >> bad values are clear enough. > > extend='both' keyword to the ColorbarBase() call, or the colorbar() > call. That is indeed the right way to do it. Eric > > Maarten > ------------------------------------------------------------------------------ Nokia and AT&T present the 2010 Calling All Innovators-North America contest Create new apps & games for the Nokia N8 for consumers in U.S. and Canada $10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store http://p.sf.net/sfu/nokia-dev2dev _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
