How to shuffle rows in pairs?

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Neuro
Neuro 2022-3-23
评论： Neuro 2022-3-23
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 个评论
Image Analyst
Image Analyst 2022-3-23
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 2022-3-23
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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回答（2 个）

Stephen23
Stephen23 2022-3-23
编辑：Stephen23 2022-3-23
Ran in:
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 2022-3-23
编辑：Arif Hoq 2022-3-23
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 个评论
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Jan
Jan 2022-3-23
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 2022-3-23
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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