How to randomly swap 2 elements in an array?
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Suppose that I have the below array:
C= [1 6 5 10 1 2 11 8 2 7 3 7 9 9]
How can I swap randomly only the elements inside the bold numbers
Assume after swap 11 and 3 : C= [1 6 5 10 1 2 3 8 2 7 11 7 9 9]
or swap 10 and " " between 9 9: C= [1 6 5 1 2 11 8 2 7 3 7 9 10 9]
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Accepted Answer
Rik
on 1 May 2019
Edited: Rik
on 1 May 2019
I'm going to assume at least one of the swap elements must be an number, and that the swapped numbers are allowed to have the same value (so you can some one 9 with another 9).
C= [1 6 5 10 1 2 11 8 2 7 3 7 9 9];
bold=[1 5 6 9 10 12 13 14];
C_temp=cell(1,2*numel(C));
C_temp(2:2:end)=num2cell(C);
valid_idx=1:numel(C_temp);
valid_idx(bold*2)=[];
swap_idx=[1 1];%invalid output to enter the loop
while ~any(mod(swap_idx,2)==0) || ... %at least 1 needs to be a number
swap_idx(1)==swap_idx(2) %the indices must be different
swap_idx=valid_idx(randperm(numel(valid_idx),2));
end
%perform swap
C_temp(swap_idx)=C_temp(swap_idx(end:-1:1));
D=cell2mat(C_temp);
clc,disp(C),disp(D)
12 Comments
Rik
on 4 May 2019
This should prevent the two swapped values to be adjacent (which swaps a value with a gap, meaning it seems the array stays the same).
while ~any(mod(swap_idx,2)==0) || ... %at least 1 needs to be a number
any(swap_idx==1) || ... %the first element (1 before the first number) isn't allowed
abs(diff(swap_idx))<=1 %the indices must be different and more than 1 appart
swap_idx=valid_idx(randperm(numel(valid_idx),2));
end
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