[Matplotlib-users] how to reverse the colorbar and its label at the same time?

[Chao Y. <cha...@gm...>]

Dear all,

Is there a way to reverse the colorbar label, the default is small value at
the bottom and big value at the top, yet I would like the big value at the
bottom and small value at the top.

all code in pylab mode.

import numpy as np
import matplotlib as mat

a = np.arange(100).reshape(10,10)
contourf(a,levels=np.arange(0,101,10))
colorbar()

in the above figure, colorbar label shows 0 at the bottom and 100 at the
top.
Yet I want the 0 at the top and the 100 at the bottom, with the same
sequence of colors in the colorbar.

One way is to reverse the cmap, and then reverse the colorbar labels at the
same time:
a = np.arange(100).reshape(10,10)
contourf(a,levels=np.arange(0,101,10),cmap=mat.cm.jet_r)
cbar = colorbar()
cbar.set_ticks(np.arange(0,101,10))
cbar.set_ticklabels(np.arange(100,-1,-10))

But the problem is, sometimes I used the customized colormap, and to
increase the contrast, I do linear transformation for the data before I
plot them.
The the data that are really used for plotting are not the same. But in the
colorbar label, I used the values before transformation. Is this
complicated case,
reverse the customized colormap could not solve the problem (unlike in the
simple example above.) Does anyone have the same experience?

Thanks et cheers,

Chao

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Chao YUE
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