How to set log intervals on a logscaled colorbar ?

Question

Benjamin 2022-8-24

评论： Dyuman Joshi 2023-9-1

Hello everyone !

I'm plotting some values on graph (with scatter), and the 'ColorScale' of my colorbar is set to 'log', like this :

I want to reduce the number of 'colors' of the colormap jet to better segment my data.

Ideally I want to segment according to log ticks of the colorbar, but I only achieve to get a linear segmentation on a log colorbar :

Is there a way to fullfill my desire ?

Thank you in advance !

Ben

Dyuman Joshi 2023-9-1

Could you please attach your code and data? Use the paperclip button to do so.

Answer 1

Nivedita 2023-9-1

Hi Benjamin!

I understand that you are trying to achieve the segmentation of your colorbar according to logscale and have the log ticks appear at the segments.

I have tried to implement the above requirement using random data in the following piece of code:

% Set the colormap and its logarithmic segmentation

cmap = jet(5); % Choose any colormap you prefer and specify the number of segments

numTicks = 6; % Number of colorbar ticks

c = colorbar;

c.Ticks = [1 10 100 1000 10000 100000];

c.TickLabels = cellstr(num2str(c.Ticks'));

colormap(cmap);

clim([1, 100000]);

set(gca, 'ColorScale','log');

You can determine the custom colormap that you wish to use in your colorbar. The various colormap options available can be found in the documentation link here: Colormap Name.
In the example provided I have used the colormap named “jet” and specified the number of segments that I require in the following brackets.
I have then set the number of tick values to 6 (for 5 segments), specified the tick values and the tick labels. For more details on Colorbar properties, you can refer to the documentation here: Colorbar appearance and behavior - MATLAB
I have set the colormap limits using the “clim” function and finally in the last line, set the “ColorScale” to “log” as mentioned.

I hope it helps!