function v = seval(z,x,y,b,c,d)
# Usage: v = seval(z,x,y,b,c,d)
#
# Evaluate natural cubic spline at z
#
# inputs:
#       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
# outputs:
#       v       values of the spline at z
# dependency:
#       locate.m

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
endfor

endfunction # seval