% problem: Example  2.6 (page 126 B.Wie's book)
%  G =  K(t_1 s+1)/(s^2*(t_2 s +1));
% construct transfer function,%
T_1 = 0.75; T_2 = 1/8; K = 4;
G = tf(K*[T_1 1], [T_2 1 0  0]) %
% compute root locus,
figure(1);
axis  equal;
rlocus(G)
grid on;%
% plot open-loop bode plot,
%
figure(2);
bode(G)
grid on;  
% Nyquist plot
figure(3)
nyquist(G)
figure(4);
nichols(G)
% gain and phase margin;
figure(5);
margin(G)
% form closed-loop transfer function
H =tf([1],[1])
Cloop = feedback(G,H)
figure(6);
bode(Cloop);
grid on;
% step input response 
figure(7);
sys = ss(Cloop);
step(sys);