function v = seval(z,x,y,b,c,d)
% Usage: v = seval(z,x,y,b,c,d)
%
% Evaluate natural cubic spline at z
%
% input:
%	z	points at which the spline is evaluated
%               they are in the range [x(1), x(length(x))]
%	x,y	coordinates to be interpolated
%	b,c,d	coefficients returned by ncspline.m
% output:
%	v	values of the spline at z
% dependency:
%	locate.m locator

n = length(z);
%
g = 1;		% initial guess of the location of z(1)
for j=1:n
    i = locate(x,z(j),g);	% locate z(j)
%   evaluate at z(j) in [x(i), x(i+1)]
    tmp = z(j) - x(i);
    v(j) = y(i)+tmp*(b(i)+tmp*(c(i)+tmp*d(i)));
    g = i;	% guess for the next location
end;