samer@4: function I=fuzzeye(n,m,sigma)
samer@4: % fuzzeye  Fuzzy nonsquare unit matrix
samer@4: %
samer@4: %          I=fuzzeye(n,m)
samer@4: %          I=fuzzeye([n m])
samer@4: %          I=fuzzeye(n,m,sigma)
samer@4: %          I=fuzzeye([n m],sigma)
samer@4: %
samer@4: % return n by m 'fuzzy' unit matrix
samer@4: % spread factor sigma is roughly in elements
samer@4: % default sigma is m/n or n/m (the larger)
samer@4: 
samer@4: if length(n)>1, 
samer@4: 	if nargin<2, 
samer@4: 		sigma=2*max([n(2)/n(1) n(1)/n(2)]); 
samer@4: 	else
samer@4: 		sigma=m;
samer@4: 	end
samer@4: 	m=n(2); 
samer@4: 	n=n(1);
samer@4: else
samer@4: 	if nargin<3, sigma=max([m/n n/m]); end
samer@4: end
samer@4: 
samer@4: sigma=sigma/max([n m]); 
samer@4: [X,Y]=meshgrid(0:m-1,0:n-1);
samer@4: X = X/(m-1);
samer@4: Y = flipud(Y)/(n-1);
samer@4: Z = ((X-Y).^2)/(sigma^2);
samer@4: I = exp(-Z/2);