s10ex44.m

Industrial Mathematics

% Routine 10.4  Nyquist plot  
W=100; 
dw = 0.1;  
w=0:dw:W; 
s= i*w;      
N = 1; 
D = 1;
H = N./D;      
N = s.*s - 2*s + 1;  
D = s.*s.*s - s.*s + s + 3  
P= N./D;  
G= H.*P;
r = abs(G);     
theta = angle(G); 
polar(theta,r,'k')
hold;
polar(-theta,r,'k--')