MATLAB: Plot two variable sum function

Question

Hi can you tell me please how can I plot with 2 variables in sum function like this?

I need graph plot(omega,theta) and plot(omega,amplitude)

Answer 1

Looks like you are translating from SMath Studio to MATLAB. The following is one way to do what you want:

% Basic data
beta(1) = 0.000125;   lambda(1) = 0.0124;
beta(2) = 0.001424;   lambda(2) = 0.0305;
beta(3) = 0.001274;   lambda(3) = 0.111;
beta(4) = 0.002568;   lambda(4) = 0.301;
beta(5) = 0.000748;   lambda(5) = 1.13;
beta(6) = 0.000273;   lambda(6) = 3;
% Define range of w
w = 0:0.001:1;
% Call function
[Amplitude, Theta] = fn(w,beta,lambda);
% Plot results
subplot(2,1,1)
plot(w,Amplitude),grid
xlabel('Omega'), ylabel('Amplitude')
subplot(2,1,2)
plot(w,Theta),grid
xlabel('Omega'), ylabel('Theta')
function [Amp, Theta] = fn(w,beta,lambda)
        
         n = numel(w);
         Amp = zeros(n,1);
         Theta = zeros(n,1);
         for i = 1:n
             Re = sum(beta./(lambda.^2 + w(i)^2));
             Im = w(i)*10^-3 + w(i)*sum(beta.*lambda./(lambda.^2 + w(i)^2));
             Amp(i) = sqrt(Re^2 + Im^2);
             Theta(i) = atan(Im/Re);
         end
 
end