Customize Colormap with unequal range of colors.

I want to have a colormap for values ranging from 0 to 5. I want values from 0 to 1.95 to be of 'white' color, 1.95 to 2.05 to be of 'blue' and 2.05 to 5 to be of 'yellow'. Its urgent. Thanks in advance!

Answer 1

[Karim]

% first create some plot data, we use the matlab peaks as example
[X,Y,Z] = peaks(100);

% rescale the Z values so that they are between 0 and 5
Z = Z + abs(min(Z(:)));
Z = (Z./max(Z(:)))*5;

% create a 'color range', we need to sample between the min and max value of
% the plot and divide the range using the greatest common divisor of the
% desired ticks 
col_range = 0:0.05:5;

% in our range look for the indexes for the colors we want
white_idx  = col_range < 1.95;
blue_idx   = col_range >= 1.95 & col_range < 2.05;
yellow_idx = col_range >= 2.05;

% initialize the color map i.e. as many rows as ticks and 3 columns (for
% the rgb values)
col_map = zeros(numel(col_range),3);

% set the colors using our previous indexes 
col_map(white_idx,:)  = repmat( [1 1 1] ,sum(white_idx),1);
col_map(blue_idx,:)   = repmat( [0 0 1] ,sum(blue_idx),1);
col_map(yellow_idx,:) = repmat( [1 1 0] ,sum(yellow_idx),1);

% create the figure
figure
surf(X,Y,Z,'EdgeAlpha',0.25)
% activate the colormap
colormap(col_map)
% get the handle for the colorbar
col_handle = colorbar;
% set the ticks to the desired values
col_handle.Ticks = [0 1.95 2.05 5];