How to set the unequal interval colorbar for colormap!

Question

ren ren 2019-5-28

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https://ww2.mathworks.cn/matlabcentral/answers/464315-how-to-set-the-unequal-interval-colorbar-for-colormap

评论： ren ren 2019-5-28

采纳的回答： Bjorn Gustavsson

Hello, how to set the colorbar as the picture shows?

The colorbar is not the equal interval!

Thanks!

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Answer 1

Bjorn Gustavsson 2019-5-28

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The QD-way I'd try first would be to make up a suitable transform of the data to map from being linear between 25 and 25 to what is desired. Something like this:

y = 1:19;                   % This defines the output of the data-transform
x = [-25:5:-5,-4:4,5:5:25]; % this is the input
d = 3*peaks(123);
dtr = d;
dtr(:) = interp1(x,y,d(:),'pchip'); % here we transform the data - only for displaying...
subplot(1,2,1)
imagesc(d)
colorbar
subplot(1,2,2)
imagesc(dtr)         
cblh = colorbar;        % and here we have to pay the price of being cunning/lazy
set(cblh,'ytick',1:19)  % and set ticks and ticklabels manually
set(cblh,'ytick',1:19,'yticklabel',num2str(x'))

HTH

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Bjorn Gustavsson 2019-5-28

That mapping simply takes the values of my d and puts values between -25 and -20 to values between 1 and 2, values between -20 and -15 will end up between 2 and 3 in the output - and so on. Therefore values between 0 and 1 will end up between 9 and 10 in the output (10 and 11, somewhere in the middle) and will occupy the same fraction of the range of output data as values between -25 and -20. If you have a book on image processing at hand you could look up histogram equalization, this is the same idea.