How do I save a colormap and use it for another figure?

I run a script and produce the following figure.

I use colormapeditor to adjust the scale (see colorbar near 0 and 1). When I do the same for another figure that has the same range of values (0 to 1) the colorbar is slightly different (0.7 is yellow in the top figure and greenish in the bottom figure):

How do I save the colormap from the first figure and apply it to another?

Thank you in advance for your help!

Best regards,

Alex

Answer 1

[Star Strider]

After you plot the first figure, use this get call:

cm = get(gca,'Colormap');

Note that the 'Colormap' (link) and the colorbar (link) object are not the same. If you want to save it and use it somewhere else, you can get its handle with:

c = colorbar;

Experiment to get the result you want.

[Stephen23]

Or simply:

cm = colormap(gca)
cm = colormap() % for the current figure

[Star Strider]

Noted.

Good point.

I tend to use gca for everything that has to do with plots.

[Alex]

Thank you both, but I don't think I'm calling the saved colormap correctly.

After I produce the first figure and adjust the colormap using colormapeditor I save it:

cm = colormap(gca)
save('colorbar.mat','cm')

I run the code again to produce the next figure, but how do I specify the colormap I've saved? This doesn't work:

load('colorbar')
figure 
h= pcolor(x,y,z); shading 'interp';
colormap(cm)
xlabel(colorbar,' \Delta n_e/n_{e_{max}}','fontsize',24, 'fontweight','bold')

[Star Strider]

I’m not certain what you’re doing. If you save it to a .mat file, you then have to load it from that file to use it again.

Note that you’re saving the colorbar object, not the colormap. They’re not the same thing.

[Alex]

I run the first dataset and crate a pcolor figure with the results:

figure 
h= pcolor(x,y,z); shading 'interp';
colormap 'jet'
xlabel(colorbar,' \Delta n_e/n_{e_{max}}','fontsize',24, 'fontweight','bold')

Now I open colormapeditor and and adjust the colorbar:

colormapeditor

I get the first figure in my question above with the corresponding colorbar. Using your answer above I try to save the colormap to a .mat file so that whenever i run this code again I can load the colorbar and apply it to other figures:

cm = colormap(gca)
save('colorbar.mat','cm')

Begin new Matlab session:

load('colorbar')
figure 
h= pcolor(x,y,z); shading 'interp';
colormap(cm)
xlabel(colorbar,' \Delta n_e/n_{e_{max}}','fontsize',24, 'fontweight','bold')

But it doesnt work.

I just wrote down the colordata minimum and maximum from the first colormapeditor and inserted it manually for the other figures. Seems to work for what I need, but surely there is a better way.

[Star Strider]

The problem is that you saved the colormap data to colorbar.m. (This is the most original illustration of ‘overshadowing’ I’ve seen in a while.) The problem is that when you thought you were loading ‘colorbar.mat’, you were actrually loading something else.

Try this instead:

cm = colormap(gca)
save('cmap.mat','cm')

then:

load('cmap');

The rest of your code should then work. It did when I ran it with these changes.

[Alex]

I hope I get points for originality. This works great. Thank you for your time and patience! I suppose that is usually the problem with computers...the user.

Me: "The computer isn't doing what I'm telling it to do."

Answer: "The computer is doing exactly what you are telling it to do! The problem is what you are telling it to do is different than what you think you are telling it to do."

[Star Strider]

As always, my pleasure!

I learned something from figuring out the problem you were having, and the solution, as well.

Your comment reminds me of a poem posted to the Stanford University computer bulletin board in the late 1970s:

I really hate this damn machine.

I wish that they would sell it.

It won’t do what I want it to,

But only what I tell it!