How to fix a colormap

Dear all,

the following toy problem

figure; hold on;
[X,Y] = meshgrid(1:0.5:10,1:20);
Z = sin(X) + cos(Y);
surf(X,Y,Z);
colorbar;
zlim([-1,1]);

generates a colored figure. I would like to keep these colores "fixed".

However, when I add another surf plot as follows

Znew = Z+5;
surf(X,Y,Znew);

the colors change.

Thanks for any help!

Answer 1

[Cris LaPierre]

Your colormap isn't changing, but by default MATLAB scales the colormap to the range of data in the plot. If your first surf plot, the Z data ranges from -2:2. So when that is the only plot, blue corresponds to -2 and yellow to 2.

[X,Y] = meshgrid(1:0.5:10,1:20);
Z = sin(X) + cos(Y);
surf(X,Y,Z);
colorbar

However, in your second surface, Znew ranges from 3 to 7. With both surfaces on the plot, blue still corresponds to -2, but now 7 corresponds to yellow. 2 now corresponds to turquoise.

Znew = Z+5;
figure
surf(X,Y,Z);
hold on
surf(X,Y,Znew);
hold off
colorbar

So before we can say how to fix the color scaling, could you explain what it is you want to happen?

[Stephan]

Thank you!

Can one change this "default" such that MATLAB scales the colormap to a specific range that one can specify?

[Cris LaPierre]

You can use the caxis function to specify the limits of your color range.

[Stephan]

Thank you!