function Y = cheby(x,p)
%CHEBY Chebyshev polynomials.
% Y = CHEBY(X,P) evaluates the first P Chebyshev polynomials
% at the vector X. The K'th column of Y contains the
% Chebyshev polynomial of degree K-1 evaluated at X.
Y = ones(length(x),p);
x = x(:); % Ensure x is a column vector.
if p == 1, return, end
Y(:,2) = x;
for k = 3:p
Y(:,k) = 2*x.*Y(:,k-1) - Y(:,k-2);
end