I am curious why the frequency vector returned in the second case below extends from 0 to 2 pi instead of from 0 to pi like in the first case. The help documentation seems to say that the first case is behaving correctly. Note: The results are correct in both cases. I am just wondering about the inconsistency. Octave 5.2.0, Windows 10.
Tony
% Poles 0.9 exp(+-j pi/4), Zero at -1
subplot(2, 1, 1)
theta_r = [-1 1]*pi/4;
a = poly(0.9*exp(j*theta_r));
b = poly(-1);
[H1 W1] = freqz(b, a);
plot(W1/pi, abs(H1))
% No poles. Zeros at angles that are multiples of pi/4 on unit circle except at angle 0
subplot(2, 1, 2)
theta_r = [-3:-1 1:4]*pi/4;
a = 1;
b = poly(exp(j*theta_r));
[H2 W2] = freqz(b, a);
plot(W2/pi, abs(H2))