MATLAB: Help With For Loops in Plotting Problem

for loopMATLAB

I have written this formula and it works well…
The thing is I need to use For loops for the values of "Zeta" to change. I need to be able to plot four graphs with values 0.2, 0.4, 0.6, 0.8 for Zeta.
Should I use the For loop on the C_t formula? or would it be better for only the value of Zeta to change? Either way I can't seem to make it work. Any suggestions on how to proceed?
Zeta=0.2;
Nat_fr=2.5;                   %Natural Frequency
Beta= sqrt(1-Zeta.^2);
Tan_theta=Beta/Zeta;
theta=atan(Tan_theta);        %Angle in radians
t= linspace(0,15,100);
%% Equation
c_t= 1-(1/(sqrt(1-Zeta.^2))).*(exp(-Zeta.*Nat_fr.*t)).*sin((sqrt(1-Zeta)).*Nat_fr.*t+atan((sqrt(1-Zeta))/Zeta));
%% Plot
plot(t,c_t)

Best Answer

temp=1;
t= linspace(0,15,100);
Nat_fr=2.5;                   %Natural Frequency
for Zeta=0.2:0.2:0.8
    Beta (temp,1)= sqrt(1-Zeta.^2);
    Tan_theta(temp,1)=Beta(temp,1)/Zeta;
    theta(temp,1)=atan(Tan_theta(temp,1));        %Angle in radians
    %% Equation
    c_t= 1-(1/(sqrt(1-Zeta.^2))).*(exp(-Zeta.*Nat_fr.*t)).*sin((sqrt(1-Zeta)).*Nat_fr.*t+atan((sqrt(1-Zeta))/Zeta));
    %% Plot
    plot(t,c_t)
    hold on
    temp=temp+1;
end
legend ('Zeta=0.2','Zeta=0.4','Zeta=0.6','Zeta=0.8');
grid on;
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