Swap 3 random elements in an array

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Amine Ne
Amine Ne on 20 Aug 2018
Commented: Amine Ne on 20 Aug 2018
How do I randomly swap three elements in an array? The element at selected position one will be moved to selected position two, the previous element at selected position two will be moved to position three, and the element at position three will be moved to selected position one.
For example: a=[4 2 3 1 5 7 6] would become anew=[4 2 6 1 3 7 5]
Thank you

Accepted Answer

Steven Lord
Steven Lord on 20 Aug 2018
Use randperm to select 3 elements (without replacement) from your vector.
a = [4 2 3 1 5 7 6]
ind = randperm(numel(a), 3)
a(ind) = a(ind([3 1 2]))

More Answers (1)

KALYAN ACHARJYA
KALYAN ACHARJYA on 20 Aug 2018
Edited: KALYAN ACHARJYA on 20 Aug 2018
% I have tried this only swap two elements or even numbers, definite swap with each other is only possible in even numbers.
a=randperm(7)
idx=randperm(3);
a(idx)=a(fliplr(idx))
I have tried in another way, you can do that
a=randperm(7)
n=randi(5);
new_array=a(:,:);
new_array([n n+1 n+2])=a([n+2 n n+1])
  4 Comments
KALYAN ACHARJYA
KALYAN ACHARJYA on 20 Aug 2018
I have added (Edited answer) another way, pls try, if OK pls confirm it
Amine Ne
Amine Ne on 20 Aug 2018
Edited: Amine Ne on 20 Aug 2018
The second solution allows to swap between 3 consecutive elements.
For example: a=randperm(7)=[7 5 4 1 2 3 6];
n=randi(5)=4; new_array=a(:,:);
new_array([n n+1 n+2])=a([n+2 n n+1])=[7 5 4 3 1 2 6]
I think it is good for me, Thank you KALYAN ACHARJYA for your help and your time.

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