How to shuffle rows in pairs?

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Neuro
Neuro il 23 Mar 2022
Commentato: Neuro il 23 Mar 2022
Hello. I have a 600 x 1 matrix. They can have only 8 values, let's say 1, 2, 3, 4, 5, 6, 7, and 8. I want to randomize the order of the rows but in pairs so 1 is always followed by 2, and 3 is always followed by 4, 5 is always followed by 6, and 7 is always followed by 8. Like there were only 4 elements: 1-2, 3-4, 5-6, and 7-8. But in pairs in rows (within the same column).
One case: if we have
1
2
3
4
5
6
7
8
One of the many randomizations would be:
5
6
1
2
7
8
3
4
Thank you!
  2 Commenti
Image Analyst
Image Analyst il 23 Mar 2022
I don't understand how the 600 and 8 relate to each other. So do the numbers 1-8 repeat each other for rows 9-16, 17-24, etc. up to 593-600? Do you want the shuffling to occur totally within the band, like rows 1-8 must still be in rows 1-8 and rows 593-600 must still be in rows 593-600? Or can any row end up anyplace except that the following row must also be moved so that it's following it in its new row location?
Neuro
Neuro il 23 Mar 2022
Sorry. 600 is the number of rows and the integers 1 to 8 are the elements - they repeat each other. I need to shuffle the elements so they are shuffled in pairs so the element 2 is always preceeded by a 1, the 4 is always preceded by a 3, and so on. Like shuffling in pairs.

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Risposte (2)

Stephen23
Stephen23 il 23 Mar 2022
Modificato: Stephen23 il 23 Mar 2022
V = 1+mod(0:599,8).' % fake data
V = 600×1
1 2 3 4 5 6 7 8 1 2
M = reshape(V,2,[]);
X = randperm(size(M,2));
V = reshape(M(:,X),[],1)
V = 600×1
1 2 7 8 3 4 5 6 5 6

Arif Hoq
Arif Hoq il 23 Mar 2022
Modificato: Arif Hoq il 23 Mar 2022
try this:
A=randi([1 8],600,1);
for i=1:size(A,1)
if A(i)==1
A(i+1)=2;
elseif A(i)==3
A(i+1)=4;
elseif A(i)==5
A(i+1)=6;
elseif A(i)==7
A(i+1)=8;
end
end
  4 Commenti
Jan
Jan il 23 Mar 2022
I'm not sure what the purpose of your code is. A shorter version:
for i = 1:size(A,1)
if A(i) < 8
A(i+1) = A(i) + 1;
end
end
This might append an element and is not a random shuffling.
Neuro
Neuro il 23 Mar 2022
Thanks, but it doesn't work. It shuffles things without following the rule (pairs of rows) and it adds one more element to the end.

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