To zoom in on the relevant section of a colorbar -- I convinced myself once that I'd need an auxiliary function to define a new cdict that covers only the current section of the original cdict. (and then define a new colorbar from the cdict, and maybe do a little norming of the data).
_segmentdata will give you the original cdict for whichever colorbar you're using. Not that I got around to actually doing it! But it would be great for paper readability and passing-around of plots. &C On Mar 27, 2010, at 9:24 PM, Ariel Rokem wrote: > Hi Friedrich, > > Thanks a lot for your response. I think that you are right - using > the vmin/vmax args into imshow (as well as into pcolor) does seem to > do what I want. Great! > > The only thing that remains now is to simultaneously stretch the > colormap in the image itself to this range, while also restricting > the range of the colorbar which is displayed, to only the part of > the colormap which actually has values (in the attached .png, I only > want values between 0 and ~0.33 to appear in the colorbar, not from > negative -0.33 to +0.33). > > Does anyone know how to do that? > > Thanks again - > > Ariel > > On Sat, Mar 27, 2010 at 3:29 PM, Friedrich Romstedt > <friedrichromst...@gmail.com > > wrote: > 2010/3/27 Ariel Rokem <aro...@berkeley.edu>: > > I am trying to make a color-map which will respond to the range of > values in > > the data itself. That is - I want to take one of the mpl colormaps > and use > > parts of it, depending on the range of the data. > > > > In particular, I am interested in using the plt.cm.RdYlBu_r > colormap. If the > > data has both negative and positive values, I want 0 to map to the > central > > value of this colormap (a pale whitish yellow) and I want negative > values to > > be in blue and positive numbers to be in red. Also - I would want > to use the > > parts of the colormap that represent how far away the smallest and > largest > > values in the data are from 0. So - if my data is in the range > [x1,x2] I > > would want to use the part of the colormap in indices > > 127-127*abs(x1)/(x2-x1) through 127+127*x2/(x2-x1). If the data only > > includes positive numbers, I would want to only use the blue part > of the > > colormap and if there are negative numbers, I would want to only > use the red > > part of the colormap (in these cases, I would also want to take > only a > > portion of the colormap which represents the size of the interval > [x1,x2] > > relative to the interval [0,x1] or [x2,0], as the case may be). > > > > I think that this might be useful when comparing matrices > generated from > > different data, but with the same computation, such as correlation > or > > coherence (see http://nipy.sourceforge.net/nitime/examples/ > fmri.html to get > > an idea of what I mean). > > I might miss something important, but why not use pcolor() with kwargs > vmin and vmax, > http://matplotlib.sourceforge.net/api/axes_api.html#matplotlib.axes.Axes.pcolor > > , > e.g.: > > maxval = numpy.abs(C).max() > pcolor(C, vmin = -maxval, vmax = maxval) > > As far as I can judge, this should have the desired effect. > > Friedrich > > > > -- > Ariel Rokem > Helen Wills Neuroscience Institute > University of California, Berkeley > http://argentum.ucbso.berkeley.edu/ariel > < > colorbar > .png > > > ------------------------------------------------------------------------------ > Download Intel® Parallel Studio Eval > Try the new software tools for yourself. Speed compiling, find bugs > proactively, and fine-tune applications for parallel performance. > See why Intel Parallel Studio got high marks during beta. > http://p.sf.net/sfu/intel-sw-dev_______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/matplotlib-users ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
