ChebyshevPoly(n)

% ChebyshevPoly.m by David Terr, Raytheon, 5-10-04

% Given nonnegative integer n, compute the 
% Chebyshev polynomial T_n. Return the result as a column vector whose mth
% element is the coefficient of x^(n+1-m).
% polyval(ChebyshevPoly(n),x) evaluates T_n(x).


function tk = ChebyshevPoly(n)

if n==0 
    tk = 1;
elseif n==1
    tk = [1 0]';
else
    
    tkm2 = zeros(n+1,1);
    tkm2(n+1) = 1;
    tkm1 = zeros(n+1,1);
    tkm1(n) = 1;

    for k=2:n
        
        tk = zeros(n+1,1);

        for e=n-k+1:2:n
            tk(e) = 2*tkm1(e+1) - tkm2(e);
        end
        
        if mod(k,2)==0
            tk(n+1) = (-1)^(k/2);
        end
        
        if k<n
            tkm2 = tkm1;
            tkm1 = tk;
        end
        
    end
    
end