Python Matplotlib Colormap
Question: I use the colormap "jet" to plot my graphics. But, I would like to have the
lower values in white color and this colormap goes from blue to red colors. I
also don't want to use another colormap because I need this range of colors...
I tried to make my colormap to get the same as "jet" with a range of values in
white, but this is too difficult. Someone could help me please? Thank you


Answer: Probably there should be an easiest solution, but the way I figured out is by
creating your own matplotlib.colors.LinearSegmentedColormap, based on the
"jet" one.

(The lowest level of your colormap is defined in the first line of each tuple
of red, green, and blue, so that's where you start editting. I add one extra
tuple to have a clearly white spot in lower part. ...for each color, in the
first element of the tuple you indicate the position in your colorbar (from 0
to 1), and in the second and third the color itself).

    
    
    from matplotlib.pyplot import *
    import matplotlib
    import numpy as np
    
    cdict = {'red': ((0., 1, 1),
                     (0.05, 1, 1),
                     (0.11, 0, 0),
                     (0.66, 1, 1),
                     (0.89, 1, 1),
                     (1, 0.5, 0.5)),
             'green': ((0., 1, 1),
                       (0.05, 1, 1),
                       (0.11, 0, 0),
                       (0.375, 1, 1),
                       (0.64, 1, 1),
                       (0.91, 0, 0),
                       (1, 0, 0)),
             'blue': ((0., 1, 1),
                      (0.05, 1, 1),
                      (0.11, 1, 1),
                      (0.34, 1, 1),
                      (0.65, 0, 0),
                      (1, 0, 0))}
    
    my_cmap = matplotlib.colors.LinearSegmentedColormap('my_colormap',cdict,256)
    
    pcolor(np.random.rand(10,10),cmap=my_cmap)
    colorbar()
    show()
    

You'll get the following: ![jet colormap with
white](http://i.stack.imgur.com/rIGWf.png)

