Help With for loop with tranfer function and step

s=tf('s');

G=1/(s^2+0.4*s+0.1);
 K=[1 2 3 4 5 6];
figure
hold on
for i=1:1:length(K)

   
T=K(i)*G;
step(T)
    S=stepinfo(T);
    L=S.Peak(T)
end

I have this code but i get the error : "Unable to use a value of type tf as an index."

I want actually to make a vector containg all the values of the peak values and only then plot the peaks with the corresponding value of gain.

Thank you in advance

Answer 1

[Sam Chak]

Hi @Davide Cannavacciuolo

You probably want to plot like this:

s = tf('s');

G = 1/(s^2 + 0.4*s + 0.1);
K = [1 2 3 4 5 6];

figure(1)
hold on
for i = 1:length(K)
    T    = K(i)*G;
    step(T)
    S    = stepinfo(T);
    L(i) = S.Peak;
end
grid on
hold off

figure(2)
plot(K, L, '-o'), grid on
xlabel('Gain'), ylabel('Peak')

[Davide Cannavacciuolo]

Thank you so much!

[Sam Chak]

Ciao @Davide Cannavacciuolo. You're welcome!

Answer 2

[Dyuman Joshi]

There is no field in the struct 'S' with name 'T'. Thus you get the error in the line you defined 'S'.

I suspect that you want to get the 'Peak' value for each system -

s=tf('s');
G=1/(s^2+0.4*s+0.1);
K=[1 2 3 4 5 6];

%Preallocation
L = K.*0;

figure
hold on

for i=1:1:length(K)
T=K(i)*G;
step(T);
S=stepinfo(T);
L(i)=S.Peak;
end

L

L = 1×6

10.7689 21.5379 32.3068 43.0757 53.8447 64.6136

[Davide Cannavacciuolo]

Thank you so much!