redblue(m)

function [c] = redblue(m)
%
% redblue  	Shades of red to white to blue colormap.
%		REDBLUE(M) returns an M-by-3 matrix containing a
%		"redblue" colormap.
%               CAVEAT this actually only works properly for even length
%               colormaps.  Some fiddling will get it to work generally.
%
%		See also HSV, COLORMAP, RGBPLOT.

if nargin<1
  [m,n] = size(colormap);
end;

m0=floor(m*0.0);
m1=floor(m*0.20);
m2=floor(m*0.20);
m3=floor(m/2)-m2-m1;

b_= [ 0.4*(0:m1-1)'/(m1-1)+0.6; ones(m2+m3,1)];
g_=  [zeros(m1,1); (0:m2-1)'/(m2-1);ones(m3,1)];
r_=  [zeros(m1,1); zeros(m2,1); (0:m3-1)'/(m3-1)];

r=[r_; flipud(b_)];
g=[g_; flipud(g_)];
b=[b_; flipud(r_)];

c=[r g b];