How to use two colormaps in one imagesc plot?

I got a correlation map 50*50 with the data range [-0.8,1], I would like to plot the map using imagesc, and set the colormap based on the value range of each pixel, e.g for value >0 using 'hot' and for value<=0 using 'cool'. Is there a simple way to achieve this? Thanks in advance!

Answer 1

[Ameer Hamza]

You can create a new colormap based on the proportion of the individual colormap

imagesc(M);
colorbar();
caxis([-0.8 1]);
cmap = [cool(80); hot(100)];
colormap(cmap);

[xw wang]

Thanks~ The problem is the the proportion of the data is not always the same across all my correlation maps, and the value is double precision, so the actual range can be [-0.8123,0.9123], and the way you suggested is not easy to make the devision at 0, am I right?

[Ameer Hamza]

You don't have to be super-precise. Something like this should work with a barely noticeable discrepancy

q = rand(1000)*1.8-0.8;
lims = [-0.8123, 0.9123];

imagesc(q);
colorbar();
caxis(lims);
lims = floor(abs(lims)*100);
cmap = [cool(lims(1)); hot(lims(2))];
colormap(cmap);

[xw wang]

Great, thanks, this seems a good way solving my problem, thanks a lot

[Ameer Hamza]

I am glad to be of help!