function yt = rbf(xt, x, w)
%RBF	calculate values at some xt.
%	yt = rbf(xt, x, w);
%
%	x: centers (2 * N)
%	w: weights (N * 1)

%	Ling Li, Caltech
%	11/11/2000

%if nargin < 2
%	x = [1     0     0    -1     0     0    -2; ...
% 	     0     1    -1     0     2    -2     0];
%	y = [-1   -1     -1     1     1     1     1];
%	w = rbfweight(x, y);
%end

yt = exp(-0.5 * dist2(xt, x)) * w;

