x = tf([1 -2 2 -1], [1 -1.7 0.8 -0.1],-1)
z = filter([1 -2 2 -1], [1 -1 0.8 -0.1], [1 zeros(1,49)]);
subplot(2,1,1)
pzmap(x);
hold on;
subplot(2,1,2)
stem(z,'filled')
title('Impulse response of system')