Assigning black color to zero values of "imagesc" plot
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I want to use "imagesc" to plot the following matrix:
A=[9 24 6 12 6;
0 33 24 0 12;
0 0 13 14 12;
0 0 0 0 0];
I want to assign black color to 0 values and set the color bar from 6 to 33.
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Accepted Answer
Image Analyst
on 24 Sep 2013
Try this:
A=[9 24 6 12 6;
0 33 24 0 12;
0 0 13 14 12;
0 0 0 0 0];
imagesc(A);
cmap = jet(max(A(:)));
% Make values 0-5 black:
cmap(1:6,:) = zeros(6,3);
colormap(cmap);
colorbar
2 Comments
Image Analyst
on 25 Sep 2013
A=[9 9.1 8.3 0 0;
0 9.5 8.4 0 0;
0 0 9.6 8.3 8.1;
0 0 0 9.7 0];
lowestValue = min(A(A(:)>0))
highestValue = max(A(:))
imagesc(A);
cmap = jet(256);
colormap(cmap);
caxis(gca,[lowestValue-2/256, highestValue]);
% Make less than lowest value black:
cmap(1,:)=[0,0,0];
colormap(cmap)
colorbar
More Answers (1)
Kelly Kearney
on 24 Sep 2013
It'll be a little tricky to do with imagesc, but you could get a similar result with pcolor:
aplt = nan(size(A)+1);
aplt(1:end-1,1:end-1) = A;
aplt(aplt == 0) = NaN;
pcolor(aplt);
colorbar;
set(gca, 'color', 'k', 'clim', [6 33], 'ydir', 'reverse')
2 Comments
Kelly Kearney
on 25 Sep 2013
Neither function does any smoothing, unless you use interpolated shading with the pcolor plot. If you're referring to the black outlines of each grid cell that is the default under pcolor, you can alter that with a simple
shading flat;
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