
x=0:0.1:2*pi;
horizontal=-1:0.001:1;
vertical=-1:0.001:1;
z=exp(j*x);

nula1r=real(exp(-j*2*pi/3));
nula1i=imag(exp(-j*2*pi/3));

nula2r=real(exp(j*2*pi/3));
nula2i=imag(exp(j*2*pi/3));

nula3r=real(exp(-j*6*pi/7));
nula3i=imag(exp(-j*6*pi/7));

nula4r=real(exp(j*6*pi/7));
nula4i=imag(exp(j*6*pi/7));

pol1r=real(0.4*exp(-j*pi/3));
pol1i=imag(0.4*exp(-j*pi/3));

pol2r=real(0.4*exp(j*pi/3));
pol2i=imag(0.4*exp(j*pi/3));

pol3r=real(0.85*exp(-j*pi/2));
pol3i=imag(0.85*exp(-j*pi/2));

pol4r=real(0.85*exp(j*pi/2));
pol4i=imag(0.85*exp(j*pi/2));



plot(nula1r,nula1i,'ro',nula2r,nula2i,'ro',nula3r,nula3i,'ro',nula4r,nula4i,'ro',pol1r,pol1i,'rx',pol2r,pol2i,'rx',pol3r,pol3i,'rx',pol4r,pol4i,'rx',cos(x),sin(x),'b',horizontal,0,'b',0,vertical,'b')


H=1-z.^-1;
f = 2*z/(z-2).^2;
h=iztrans(H)