how to change the scale of an colour bar?

Hello, My plot range with variation from 0 to 3500, so I want to use an log scale colour bar instead of normal colour bar scale, so that I can show all the variations. please give some suggestion to change the colour scale of the colorbar into an log scale.

Answer 1

[Robert U]

Hi Puspa patra,

I google'd it for you and found:

• https://de.mathworks.com/matlabcentral/answers/203697-logarithmic-scale-for-colorbar
• https://de.mathworks.com/matlabcentral/answers/100066-how-do-i-create-a-logarithmic-scale-colormap-or-colorbar
• https://de.mathworks.com/matlabcentral/answers/393174-how-can-i-make-a-logarithmic-color-plot-and-colorbar

Depending on Matlab version, you can go with different approaches. Known from older versions (prior 2018a):

% Create testdata
Data=magic(100);
% Define color levels to create
nLvl = 9;
% get min and max values of Data
minData = min(min(Data));
maxData = max(max(Data));
% define colorbar values on log scale
c = logspace(log10(minData),log10(maxData),nLvl);
% plot data in log-scale according to defined log scale values 'c'
contourf(log(Data),log(c));
% Change colormap to "bone"
colormap(bone);
% define color axis scaling according to 'c'
caxis(log([c(1) c(end)]));
% open colorbar
colorbar('YTick',log(c),'YTickLabel',c);

Kind regards,

Robert