Colorbar in colormap with labels

Question

erup eruo 2018-10-26

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回答： erup eruo 2018-10-26

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!!

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Answer 1

jonas 2018-10-26

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编辑：jonas 2018-10-26

在 MATLAB Online 中打开

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]);

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Answer 2

erup eruo 2018-10-26

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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.

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jonas 2018-10-26

编辑：jonas 2018-10-26

在 MATLAB Online 中打开

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 2018-10-26

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

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Answer 3

erup eruo 2018-10-26

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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!!

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jonas 2018-10-26

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

Image Analyst 2018-10-26

Vote for it too, like I did.

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