function Sbar = NRTCRR(S0, up, down, N)
% Octave/MATLAB function to compute the binary non-
% recombining tree of underlying asset prices from a
% spot price and constant up and down factors.
% INPUTS: (Example)
% S0 = asset spot price (100)
% up = up factor (1.2)
% down = down factor (0.8)
% N = binomial tree height, must be >=0 (3)
% OUTPUT:
% Sbar = tree as linear array Sbar(m), 0