How can I save data from for loop?

Question

majid 2024-4-13

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回答： Vaibhav 2024-7-25

Hello.

I have 3 arrays of scalar number. I want to have some simple calculation on all numbers of these 3 arrays one by one (Permutation of all arrays numbers ), then multiplying every result (y) with rand(4,20) and finally saving every result as a excel data. I wrote the below codes but I have some problem: "I see in the output only the last multipication result of y" and therefore just last w.

clc
clear all
i=0;
j=1;
n=1;
A = [10 20 30 40 50 10];
B = [1 1.2 1.4 1.6 1.8 1];
C = [5 25 45 65 85 5];
z= rand(4,20);
for a = 1:125
    i=i+1; 
    if i==6 
        j=j+1;
        i=1;
    end
    
    if j==6 
        n=n+1;
        j=1;
    end
    
    if(n==6) 
        n=1;
        break ;
    end
    
    A_2   =   A(i);
    B_2   =   B(j);
    C_2   =   C(n);
    
    y = A_2 * B_2 * C_2 - A_2 * C_2;
    w = y * z;
end

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Dyuman Joshi 2024-4-13

"I see in the output only the last multipication result of y" and therefore just last w."

Preallocate w and use indexing (i.e. loop variable a) to save the values in it.

majid 2024-4-13

thankyou for your answeing.

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Answer 1

Vaibhav 2024-7-25

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Hi Majid

Code is overwriting the variable w in each iteration of the loop, so only the result from the last iteration is saved. To store all the results, you can save each w in a cell array or a 3D matrix. Below is a modified version of your code that saves each result in a cell array.

clc;
clear all;
i = 0;
j = 1;
n = 1;
A = [10 20 30 40 50 10];
B = [1 1.2 1.4 1.6 1.8 1];
C = [5 25 45 65 85 5];
z = rand(4,20);
% Initialize cell array to store results
results = cell(125, 1);
for a = 1:125
    i = i + 1; 
    if i == 6 
        j = j + 1;
        i = 1;
    end
    
    if j == 6 
        n = n + 1;
        j = 1;
    end
    
    if n == 6 
        n = 1;
        break;
    end
    
    A_2 = A(i);
    B_2 = B(j);
    C_2 = C(n);
    
    y = A_2 * B_2 * C_2 - A_2 * C_2;
    w = y * z;
    
    % Store the result in the cell array
    results{a} = w;
end