How can i plot zero and its frequency responsE

How can i plot zero and its frequency response

b = conv([1 -1.08 0.3132],[1 -1.315 0.6182])
c =b;
a = [0 0 0 0.0686]
[z,p,K] = tf2zp(c,a);
figure(1)
zplane(a,c)
xlabel('Re(z)');
ylabel('Im(z)');
title('POLE DIAGRAM OF THE TRANSFER FUNCTION H(z)')
w = -pi:(pi/500):pi;
H = freqz(a,c,w);
figure(2)
subplot(2,1,1); 
plot(w, abs(H),'r','LineWidth',2);
grid on;
xlabel('frequency in pi units');
ylabel('Magntiude');
title('MAGNITUDE FREQUENCY RESPONSE OF THE TRANSFER FUNCTION H(z)')
subplot(2,1,2);
plot(w, angle(H),'r', 'LineWidth',2);
grid on;
xlabel('frequency in pi units');
ylabel('phase');

[Azzi Abdelmalek]

Paul, why are you changing your question?

Answer 1

[Azzi Abdelmalek]

The numerator should be

a = 0.0686

To find poles and zeros

[z,p,K] = tf2zp(a,c); % not tf2zp(c,a)

Add

b = conv([1 -1.08 0.3132],[1 -1.315 0.6182])
c =b;
a = 0.0686
[z,p,K] = tf2zp(a,c);
figure(1)
zplane(a,c)
xlabel('Re(z)');
ylabel('Im(z)');
title('POLE DIAGRAM OF THE TRANSFER FUNCTION H(z)')
w = -pi:(pi/500):pi;
H = freqz(a,c,w);
figure(2)
subplot(2,1,1); 
plot(w, abs(H),'r','LineWidth',2);
grid on;
xlabel('frequency in pi units');
ylabel('Magntiude');
title('MAGNITUDE FREQUENCY RESPONSE OF THE TRANSFER FUNCTION H(z)')
subplot(2,1,2);
plot(w, angle(H),'r', 'LineWidth',2);
grid on;
xlabel('frequency in pi units');
ylabel('phase');

[Azzi Abdelmalek]

I don't know what yoy did, copy and paste the added answer

[Azzi Abdelmalek]

Paul commented

Hi Azzi Abdelmalek Can you please help me with this one.I'm new to MAT LAB.

[Azzi Abdelmalek]

The frequency interval is not well chosen. It should be

w = -2*pi:(pi/500):2*pi