clear all

clr

H=tf([1 -1 -2],[1 1.5 -1],1);

poles_H=roots([1 1.5 -1])

syms z

Y(z)=(z/(z-1))*((z^2-z-2)/(z^2+1.5*z-1))

y_n=iztrans(y)

n=0:1:6

y_n_7=double(subs(y_n))

stem(n,y_n_7,'linewidth',2)

grid on

ylim([-20 40])

xlim([-1 7])

xlabel ('Samples (n)')

ylabel ('Value')

title ('First 7 samples of step response')

I was trying to use this code in octave but some commands were not possible because they belong to Matlab. An expert helped me out and solved 95% of my problems, but I am still having problem with H. H=tf([1 -1 -2],[1 1.5 -1],1);

New code that work 95%

clear all

H=tf([1 -1 -2],[1 1.5 -1],1);

poles_H=roots(poly(H)) % Find the poles of H

Y=@(z) (z./(z-1)).*((z.^2-z-2)./(z.^2+1.5*z-1));

y_n=ifft(Y(exp(2*pi*1i*(0:6)/7))); % Compute the first 7 samples of the step response

n=0:1:6;

y_n_7=real(y_n);

stem(n,y_n_7,'linewidth',2)

grid on

ylim([-20 40])

xlim([-1 7])

xlabel('Samples(n)')

ylabel('Value')

title('First 7 samples of step response')