num=[1 1];
den=[0.01 0.5 3 -10 10];
A=tf(num,den);
figure(1);
nyquist(A);
num_t= 4;
den_t = [1 1];
tau = 0.5;
A_t=tf(num,den);
set(A_t,'outputDelay',tau);
nyquist(A_t);