quantized colorbar

I would like a colorbar that only shows the colors of numbers that exist in the dataset.

Example:

x = -2*pi:0.01:2*pi;
y = x;
[X Y] = meshgrid(x,y);
Z = sign(round(cos(X).*cos(Y)));
imagesc(x,y,Z);colorbar;

There are only 3 possible numbers in the output matrix. Unfortunately, the colorbar will still show a full gradient.

I would appreciate a method for generating a colorbar with only the levels that are present.

[Sean de Wolski]

+1, well worded clear and concise question

Answer 1

[Sean de Wolski]

X = sign(round((rand(10)-.5)*2));
imagesc(X);
un_X = unique(X);
colormap(cool(length(un_X)));
H = colorbar;
set(H,'ytick',un_X);

Manually set the colormap and the colorbar's ytick to the unique values of X.

[Walter Roberson]

I read the question as asking that only the colors actually present in the image appear in the colorbar, not that only those ones are labelled.

[Sean de Wolski]

I saw that after I posted, see edit.

[Jonathan]

Answered both the question I had, and the one I hadn't thought of.

Thank you