h = [-4, 1, -1, -2, 5, 6, -6, -5, 2, 1, -1, 4];

M = length(h); n = 0:M-1;

[Hr, w, d, L] = Hr_Type4(h);

d

L

dmax = max(d) + 1; dmin = min(d) - 1;

figure('NumberTitle', 'off', 'Name', 'Exameple 7.7')

set(gcf,'Color','white'); 

subplot(2,2,1); stem(n, h); axis([-1, 2*L+1, dmin, dmax]); grid on;

xlabel('n'); ylabel('h(n)'); title('Impulse Response');

subplot(2,2,3); stem(1:L, d); axis([-1, 2*L+1, dmin, dmax]); grid on;

xlabel('n'); ylabel('d(n)'); title('d(n) coefficients');

subplot(2,2,2); plot(w/pi, Hr); grid on;

xlabel('frequency in \pi units'); ylabel('Hr'); title('Type-4 Amplitude Response');

subplot(2,2,4); zplane(h); grid on;

xlabel('real axis'); ylabel('imaginary axis'); title('Pole-Zero Plot');