function c = profilecolors(green_val, yellow_val, red_val, v)
%PROFILECOLORS Returns an interpolated RGB vector for use in CCAs.
%   PROFILECOLORS(green_val, yellow_val, red_val, v) returns an RGB matrix
%		where the position of v relative to green_val, yellow_val, and red_val
%		to obtain a point along the red-green color spectrum.  The algorithim
%		uses a two sided linear interpolation about yellow_val.  If v is outside
%		the limits of green_val or red_val, v is assigned exactly green or
%		yellow, as appropriate, thus bounding the range of assigned colors.
%		The following colors are used as boundaries for interpolation:
%			red = [1 0 0]
%			green = [0 .5 0]
%			yellow = [1 1 0]
%		Because yellow_val can be specified, both pure linear interpolation
%		across the entire range (set yellow_val = mean(green_val,red_val) or 
%		asymmetric interpolation across yellow_val can be performed.
%
% Written by Finny Kuruvilla, v1.2.3 Last modified 9-6-2000


if (yellow_val <= min(green_val,red_val)) | (yellow_val >= max(green_val, red_val))
   error('The yellow value is not between the red and green values.');
end

if (v < min(green_val, red_val))
	v = min(green_val, red_val);
elseif (v > max(green_val, red_val))
	v = max(green_val, red_val);
end

if (red_val > green_val)
   if v <= yellow_val
      c = [(v-green_val)/(yellow_val-green_val)...
            (1-(1-(v-green_val)/(yellow_val-green_val))*.5) 0];
   else
   	c = [1 (red_val-v)/(red_val-yellow_val) 0];
   end
else
   if v <= yellow_val
   	c = [1 (v-red_val)/(yellow_val-red_val) 0];
   else
      c = [(green_val-v)/(green_val-yellow_val)...
            (1-(1-(v-green_val)/(yellow_val-green_val))*.5) 0];
   end
end