Imagesc defining only 3 colours for my entire data

hi i have a matrix that is 500x600 within this i have data values ranging from 0.2 to -0.2

i have looked at user the figure colour map editor but i cannot get my desired results.

i am hoping to set out a plot with these distinctive properties for the values:

0.2>x> 0.07 - Red
0.07>x>0 - green
x = 0 - Blue
0>x>-0.07 - Green
-0.07>x>0.2 - Red

is there anyway to alter the plot to show the results in this manner?

thanks for any help Kyle

figure(i)
subplot(3,1,1);
imagesc(ux);
axis equal off
colorbar

Answer 1

[Image Analyst]

Make a 256 row colormap. Then determine the index where the changes happen. For example 0 is at row 128, and 0.07 is at row 129 or whatever. Then make up the colormap and apply it

myColorMap(0:row1, :) = [1,0,0]; % Red
myColorMap(row1+1:127, :) = [0,1,0]; % Green
myColorMap(128,:) = [0, 0, 1]; % Blue

and so on.

[kyle lyth]

im not the best withmatlab so will need to spend some time having a look at this but thanks for your reply

i did however come up with a trivial solution where i searched the matrix 1 element at a time and replaced it with a new value for each of my colour options:

lx=0;
for x=1:LX-1
  lx=lx+1;
  ly=0;
  for y = 1:LY-1
    ly = ly+1;
    if ux(ly,lx)<0.3 && ux(ly,lx)>=0.07
      ux(ly,lx)=0.2;
    elseif ux(ly,lx)<0.07 && ux(ly,lx)>0
      ux(ly,lx)=.1;
    elseif ux(ly,lx)<0.0 && ux(ly,lx)>-0.07
      ux(ly,lx)=.1;
    elseif ux(ly,lx)<=-0.07 && ux(ly,lx)>-0.3
      ux(ly,lx)=.2;
      % 0.2>x> 0.07  Red
      % 0.07>x>0 - green
      %x = 0 - Blue
      %0>x>-0.07 - Green
      %-0.07>x>0.2 - Red
    end
  end
end

[Image Analyst]

That can be vectorized into 3 faster lines. But anyway, I don't see how that applies colors.