storing output (which are matrices) of for loops

Question

Sumera Yamin 2018-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/404281-storing-output-which-are-matrices-of-for-loops

评论： Sumera Yamin 2018-6-6

Hello, I am trying to store my output from for loop to be used later in code. The output is a 2x4 matrix for each cycle of loop. here is my code.

B= [0.0250; 0.0500; 0.0750; 0.1000; 0.1250; 0.1500; 0.1750; 0.2000;    0.2250; 0.2500; 0.2750; 0.3000; 0.3250; 0.3500; 0.3750; 0.4000];
rig=0.01
for j=1:length(B)                          
k= B(j)/(2*rig)                      
TMP=        [cos(k*l)^2,          (sin(k*l)*cos(k*l))/k,       sin(k*l)*cos(k*l),         (sin(k*l)^2)/k;      
         -k*sin(k*l)*cos(k*l),          cos(k*l)^2,              -k*sin(k*l)^2,          sin(k*l)*cos(k*l); 
          -sin(k*l)*cos(k*l),         -(sin(k*l)^2)/k,             cos(k*l)^2,         (sin(k*l)*cos(k*l))/k;
              k*sin(k*l)^2,          -sin(k*l)*cos(k*l),       -k*sin(k*l)*cos(k*l),        cos(k*l)^2]
TM= TMP*TMP 
C1=[TM(1,:);TM(3,:)] 
end

I want to store C1 and k for each cycle of loop to be used later in other parts of code. please let me know what would be the best way to do so. I tried to do it by initializing an array (like we do for scalar outputs but this did not workout. Thank you very much for your help.

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Answer 1

Stephen23 2018-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/404281-storing-output-which-are-matrices-of-for-loops#answer_323443

编辑：Stephen23 2018-6-6

在 MATLAB Online 中打开

Array preallocation works for me:

l = 1;
B = [0.0250; 0.0500; 0.0750; 0.1000; 0.1250; 0.1500; 0.1750; 0.2000; 0.2250; 0.2500; 0.2750; 0.3000; 0.3250; 0.3500; 0.3750; 0.4000];
B = 0.025:0.025:0.4;
kV = nan(1,1,numel(B));
CM = nan(2,4,numel(B));
rig = 0.01;
for j = 1:numel(B)                          
    k = B(j)/(2*rig);                     
    TMP = [cos(k*l)^2,        (sin(k*l)*cos(k*l))/k, sin(k*l)*cos(k*l),    (sin(k*l)^2)/k;      
        -k*sin(k*l)*cos(k*l), cos(k*l)^2,            -k*sin(k*l)^2,        sin(k*l)*cos(k*l); 
        -sin(k*l)*cos(k*l),   -(sin(k*l)^2)/k,       cos(k*l)^2,           (sin(k*l)*cos(k*l))/k;
        k*sin(k*l)^2,         -sin(k*l)*cos(k*l),    -k*sin(k*l)*cos(k*l), cos(k*l)^2];
    TMP = TMP*TMP;
    CM(:,:,j) = [TMP(1,:);TMP(3,:)];
    kV(j) = k;
end

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Sumera Yamin 2018-6-6

Thank you very much for your help

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Answer 2

Ankita Bansal 2018-6-6

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编辑：Ankita Bansal 2018-6-6

在 MATLAB Online 中打开

Hi Sumera, you can do so by changing k to k(j) and C1 to C1(:,:,j).

B= [0.0250; 0.0500; 0.0750; 0.1000; 0.1250; 0.1500; 0.1750; 0.2000;    0.2250; 0.2500; 0.2750; 0.3000; 0.3250; 0.3500; 0.3750; 0.4000];
rig=0.01
for j=1:length(B)                          
k_1(j)= B(j)/(2*rig)   
k=k_1(j);
TMP=        [cos(k*l)^2,          (sin(k*l)*cos(k*l))/k,       sin(k*l)*cos(k*l),         (sin(k*l)^2)/k;      
         -k*sin(k*l)*cos(k*l),          cos(k*l)^2,              -k*sin(k*l)^2,          sin(k*l)*cos(k*l); 
          -sin(k*l)*cos(k*l),         -(sin(k*l)^2)/k,             cos(k*l)^2,         (sin(k*l)*cos(k*l))/k;
              k*sin(k*l)^2,          -sin(k*l)*cos(k*l),       -k*sin(k*l)*cos(k*l),        cos(k*l)^2]
TM= TMP*TMP 
C1(:,:,j)=[TM(1,:);TM(3,:)] 
end