How to shuffle rows in pairs?

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!

[Image Analyst]

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]

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.

Answer 1

[Stephen23]

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

Answer 2

[Arif Hoq]

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

[Jan]

Omit the "continue" statements, because they are not needed.

[Arif Hoq]

thanks Jan. even i did not notice that one.

[Jan]

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]

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.