b=[0.025 -0.07 0.05 -0.02];
a=[1 1.5 1.75 1.02 0.4];
poles=roots(a)			%find poles
zeros=roots(b)			%find zero
zplane(b,a)				%plot poles and zeros
title('Poles and Zeros')
[H,w]=freqz(b,a,512);	%find frequency response
figure(2)
freqzplot(H,w,'Hz')		%plot frequency response
title('Frequency Response')
[h,t]=impz(b,a,35);		%find impulse response
figure(3)
stem(t,h)					%plot imp. response in dicrete time
title('Impulse Response')
xlabel('Time  (s)')
ylabel('h(n)')
