h = [1, 2, 3, 4, 3, 2, 1]/15;
M = length(h); n = 0:M-1;
[Hr, w, a, L] = Hr_Type1(h);
a
L

amax = max(a) + 1; amin = min(a) - 1;

figure(‘NumberTitle‘, ‘off‘, ‘Name‘, ‘Exameple 7.21‘)
set(gcf,‘Color‘,‘white‘); 

subplot(2,2,1); stem(n, h); axis([-1, 2*L+1, amin, amax]);
xlabel(‘n‘); ylabel(‘h(n)‘); title(‘Impulse Response‘); grid on;

subplot(2,2,3); stem(0:L, a); axis([-1, 2*L+1, amin, amax]);
xlabel(‘n‘); ylabel(‘a(n)‘); title(‘a(n) coefficients‘); grid on;

subplot(2,2,2); plot(w/pi, Hr); grid on;
xlabel(‘frequency in \pi units‘); ylabel(‘Hr‘); title(‘Type-1 Amplitude Response‘);

subplot(2,2,4); zplane(h); grid on;
xlabel(‘real axis‘); ylabel(‘imaginary axis‘); title(‘Pole-Zero Plot‘);