Adding loop values to an array

Hello,

I'm trying to perfom a simulation that will calculate a value for a given input and then store than input in an array such that I can graph it. However, i can't seem to be able to store the values in an array. I'm brand new to MATLAB.

Any help would be greatly appreciated.

PS, I have tried to comment the code and make what I want to happen as clear as possible.

PPS, please note, should result in a real and imaginery part.

ctc, clear

%declaring variables 

rho = 1.22; 
c0 = 344;   
fillRat = 0.098;   
dampRat = 0.03;     
Fr = 417;  
K = rho*(c0)^2; 
Kr = rho*(c0)^2; 


%%calcaulating Keff

%define mamFrequency range: 
mamFrequency =  200 : 600;

%Loop through each value of mamFrequency

for j = mamFrequency
   
    omegR = j/Fr; %dependancy--

    Keff = K/((1 - fillRat) + (K/Kr)*(fillRat/(1 + 2i * dampRat * omegR - (omegR)^2)));%analytical equation
    
    %calculating Keff/K
    
    modulRat = Keff/K; %want to store modulRat value for each iteration of so can plot later
 
end

%plotting modulRat (y-axis) against i - the mamFrequency value (x-axis)
figure(1)
plot(j,modulRat); 

Answer 1

[Richard Fiifi Annan]

This is an improved version of VBBV's answer. Just like he mentioned, it plots only the real part by default. Make your choice!

CHOICE 1:

% iteration for each value of mamFrequency:

modulRat = zeros(length(mamFrequency), 1); % memory pre-allocation

for j = 1:length(mamFrequency)

omegR = (mamFrequency(j)/Fr);

Keff = K/((1 - fillRat) + (K/Kr)*(fillRat/(1 + 2i * dampRat * omegR - (omegR)^2)));%analytical equation

modulRat(j,1) = Keff/K;

end

% plotting the result:

figure

plot(mamFrequency, modulRat)

CHOICE 2:

% iteration for each value of mamFrequency:

modulRat = cell(length(mamFrequency), 1); % memory pre-allocation

for j = 1:length(mamFrequency)

omegR = (mamFrequency(j)/Fr);

Keff = K/((1 - fillRat) + (K/Kr)*(fillRat/(1 + 2i * dampRat * omegR - (omegR)^2)));

modulRat{j,1} = Keff/K;

end

modulRat = cell2mat(modulRat); % convert cell to matrix

% plotting the result

figure

plot(mamFrequency, modulRat)

[Richard Fiifi Annan]

Memory pre-allocation speeds up the computation. You will appreciate it if you have a very large matrix or vector.

[Joshua Tshuma]

Awesome! Thank you both! The code is working well, with an expected output for the real part. Would you know how I can compute the imaginary part?

Answer 2

[Richard Fiifi Annan]

real_part = real(modulRat );

imaginary_part = imag(modulRat );

figure

plot(mamFrequency, real_part, 'r', mamFrequency, imaginary_part,'b')

legend({'real part', 'imaginary part'})