create a custom colormap

hi all,

I would like to customize a colormap with specified color for each value range (from -4 to 2, a total of 7 intervals, and assign a color for each interval):

% a three-column matrix of RGB triplets for each interval:

map = [0.4940 0.1840 0.5560

0.8500 0.3250 0.0980

0.9290 0.6940 0.1250

1 1 0

0.4660 0.6740 0.1880

0 0.75 0.75

0 0.5 0];

% here is part of my codes:

image = imshow(x);

......

caxis([-4 2])

colorbar('Ticks',[-4 -3 -2 -1 0 1 2],...

'TickLabels',{'-4','-3','-2','-1','0','1','2'})

colormap(map)

The location of the label tick is not on the boundary between two color and I don't know how to fix it. Does anyone have an idea on this question?

Answer 1

[Ameer Hamza]

Because there are 6 unit-sized intervals between -4 and 2, you should use 6 colors in the map. Try this

map = [0.4940 0.1840 0.5560
    0.8500 0.3250 0.0980
    0.9290 0.6940 0.1250
    1 1 0
    0.4660 0.6740 0.1880
    0 0.75 0.75];