function [r] = bartlett(y)
%Calcluates Bartletts estimate
N = length(y);
r = zeros(2*N+1, 1);
for k = -N:N
    temp_sum = 0;
    for n = 1:(N-abs(k))
        temp_sum = temp_sum + y(n + abs(k)).*y(n);
    end
    r(k+N+1) = temp_sum/N;
end
end