How to cycle through elements in an array in Matlab

Question

Alif Aiman Ahmad Zukiman 2024-4-19

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https://ww2.mathworks.cn/matlabcentral/answers/2108896-how-to-cycle-through-elements-in-an-array-in-matlab

评论： Alif Aiman Ahmad Zukiman 2024-4-19

Hello there, I am trying to cycle through the elements in an array given a specified number of iterations. For other languages where the first element is 0, I can easily utilize the modulo command and so when the iteration is equal to the modulo it will evaluate to 0 and the array in question will start from the beginning again. However, with MATLAB, since the elements start with 1, I cannot utilize the same idea. How do I get around this? And very much possibly without the use of if else anywhere. Thank you!

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Answer 1

the cyclist 2024-4-19

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编辑：the cyclist 2024-4-19

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You can utilize the same idea. Just offset by one inside outside mod():

A = [2 3 5 7];
% Illustrate the mod() cycle with offset
for iteration = 1:8
    idx = mod(iteration-1,length(A))+1
end
idx = 1
idx = 2
idx = 3
idx = 4
idx = 1
idx = 2
idx = 3
idx = 4
% Index into the array
for iteration = 1:8
    idx = mod(iteration-1,length(A))+1;
    A(idx)
end
ans = 2
ans = 3
ans = 5
ans = 7
ans = 2
ans = 3
ans = 5
ans = 7

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Alif Aiman Ahmad Zukiman 2024-4-19

ah excellent. Thank you!

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Answer 2

Voss 2024-4-19

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https://ww2.mathworks.cn/matlabcentral/answers/2108896-how-to-cycle-through-elements-in-an-array-in-matlab#answer_1444116

To account for indexing in MATLAB starting with 1, subtract 1 from the iteration number, perform mod(), then add 1 to the result.

idx = mod(iteration-1,N)+1;

That will give idx values starting with 1 when iteration is 1, and as iteration increases, idx increases to N and then repeats starting with 1 again when iteration is N+1, and so on.