x = randn(1000,1); % 1000 Gaussian deviates ~ N(0,1)
y = filter([1 -1 1],1,x); % Create an MA(2) process
[acf,lags,bounds] = autocorr(y);
stem(lags,acf); xlabel('Lag'); ylabel('\rho(k)');
hold on;
h = line(lags,bounds(1)*ones(length(acf),1));
h1 = line(lags,bounds(2)*ones(length(acf),1));
set(h,'color',[1 0 0]);
set(h1,'color',[1 0 0]);
