Colorbar in colormap with labels

Hello,

I have this simple example where the colorbar is not working properly. For example, the color corresponding to 'j' is not shown wether the color coreesponding to 'h' (not present in the representing matrix) is.

    labels = {'a','b','c','d','e','f','g','h','i','j','k','l'};
    mtx = [2 5 4 5 6 3 2 5 2 2 2 4 6 7 9 10 9 5 9 7 10 2 3];
    t = (0:1:length(mtx)-1)/5;
    y = ones(1,length(t));
    [C,ia,ic] = unique(mtx);

    figure
    colormap(jet(length(C)));
    image(t,y,mtx); % or imagesc instead
    yticklabels({}); 
    colorbar('XTick',0:1:12,'TickLabels',labels,'Position',[0.95 0.1 0.01 0.5]);

Can anyone help me??

Tanks!!

Answer 1

[jonas]

There range in your plotted values are 2-10, and the colorscale is per default scaled so that the maximum (10) and minimum (2) are the max and min values on your colormap. You need to force the colorbar to extend beyond these values.

labels = {'a','b','c','d','e','f','g','h','i','j','k','l'};
mtx = [2 5 4 5 6 3 2 5 2 2 2 4 6 7 9 10 9 5 9 7 10 2 3];
t = (0:1:length(mtx)-1)/5;
y = ones(1,length(t));
set(gca,'clim',[0 12])

figure
cmap=colormap(jet(numel(labels)));
image(t,y,mtx); % or imagesc instead
yticklabels({});
cb=colorbar('XTick',1.5:1:12.5,'TickLabels',labels,'Position',[0.95 0.1 0.01 0.5],'limits',[1 13]);

Answer 2

[erup eruo]

That's right. But there is neither 12 nor 8 nor 11. With these limits, the labels don't correspond with the colors. Even though, 9 has the same colour than 10.

[jonas]

maybe if you change this line

colormap(jet(numel(labels)));

You need the same number of (1) colors in your colormap, (2) ticks on your colorbar and (3) number of labels

In your original script you had 12 ticklabels, 13 ticks and ~8-9 colors in your map. If you have more ticks than ticklabels, then the ticklabels start repeating. If you have less colors than ticklabels, then they will not match in the colorbar.

I guess this is what you might want as end-result

[jonas]

Come on.. don't accept your own "answer" that isn't even an answer.

Answer 3

[erup eruo]

Okey

thanks for your info

    labels = {'a','b','c','d','e','f','g','h','i','j','k','l'};
    mtx = [2 5 4 5 6 3 2 5 2 8 2 2 4 6 7 9 10 9 5 9 7 10 2 3 11 12];
    t = (0:1:length(mtx)-1)/5;
    y = ones(1,length(t));

    figure
    colormap(jet(numel(labels)));
    image(t,y,mtx); yticklabels({});

    colorbar('XTick',1.5:1:12.5,'TickLabels',labels,'Position',[0.95 0.1 0.01 0.5],'limits',[1 13]);
    set(gca,'clim',[1 12]);

Fyi, this is how I wanted the final result.

THANK YOU VERY MUCH!!

[jonas]

Yep, you can thank me by accepting the answer I provided.

[Image Analyst]

Vote for it too, like I did.

People who help you can earn "reputation" points when people Accept their answers (4 points) or vote for them (2 points). You can do both if you were the original poster. See here: https://www.mathworks.com/matlabcentral/answers/help?s_tid=al_priv#reputation

Answer 4

[erup eruo]

I'm sorry. I made a mistake. Obviously your answer is the good one