How randomly choose pairs of elements from a squared matrix and put them in an other matrix?

Question

Lorenz 2013-6-11

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/78724-how-randomly-choose-pairs-of-elements-from-a-squared-matrix-and-put-them-in-an-other-matrix

Hi, I have a matrix A

A =
   4     2     3
   3     1     2
   2     4     1
   1     3     4

How to make different groups of two elements from this matrix? But the chosen elements (from the matrix A) have to be adjacent in the matrix A. for example A(1,1) & A(1,2) are adjacent and so they can be chosen. and A(1,1) & A(4,3) can't be chosen to make a group. I'd like to create a function which randomly choose these elements from A. And the function generates an other matrix containing the (2 by 2) different groupements randomly created.

example "function group":

V=group(A)
V=  1 4
2
2
1
1
3
2
4

This new V matrix is made of groups

A(1,1)&A(2,1)
A(2,2)&A(4,1)
A(1,2)&A(1,3)
...

Hope you understand what I mean. In fact we randomly choose pairs of elements in the matrix A. thank you!

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Answer 1

Azzi Abdelmalek 2013-6-11

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/78724-how-randomly-choose-pairs-of-elements-from-a-squared-matrix-and-put-them-in-an-other-matrix#answer_88481

编辑：Azzi Abdelmalek 2013-6-11

在 MATLAB Online 中打开

m=5
n=numel(A)
ii=0
while ii<m
  id=randperm(16);
  [ii1,jj1]=ind2sub(size(A),id(1));
  [ii2,jj2]=ind2sub(size(A),id(2));
  if and(abs(ii1-ii2)<=1,abs(jj1-jj2)<=1);
      ii=ii+1;
      B(ii,:)=[A(id(1)) A(id(2))]
  end
end

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Azzi Abdelmalek 2013-6-11

编辑：Azzi Abdelmalek 2013-6-11

在 MATLAB Online 中打开

m=5
n=numel(A)
ii=0
while ii<m
id=randperm(16);
[ii1,jj1]=ind2sub(size(A),id(1));
[ii2,jj2]=ind2sub(size(A),id(2));
if and(abs(ii1-ii2)<=1,abs(jj1-jj2)<=1);
    ii=ii+1;
    B(ii,:)=[A(id(1)) A(id(2))]
    indice1{ii,1}=[ii1 jj1]
    indice2{ii,1}=[ii2 jj2]
end
end
[cell2mat(indice1) cell2mat(indice2)]

Lorenz 2013-6-11

THANK YOu very much. But I am sorry, there is just one problem I just forgot to mentionate. The chosen elements must be adjacent but not "diagonnaly adjacent", and they must be chosen just ONE TIME (the chosen elements can't be REchoose). So, at the end, I have to get only 8 pairs.

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Answer 2

Azzi Abdelmalek 2013-6-11

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/78724-how-randomly-choose-pairs-of-elements-from-a-squared-matrix-and-put-them-in-an-other-matrix#answer_88486

编辑：Azzi Abdelmalek 2013-6-11

在 MATLAB Online 中打开

m=5
n=numel(A)
ii=0
idx=[];
while ii<m
  id=setdiff(randperm(16),idx,'stable');
  [ii1,jj1]=ind2sub(size(A),id(1));
  [ii2,jj2]=ind2sub(size(A),id(2));
  if or(abs(ii1-ii2)==1 & abs(jj1-jj2)==0,abs(ii1-ii2)==0 & abs(jj1-jj2)==1);
      ii=ii+1;
      idx=[idx id(1:2)];
      B(ii,:)=[A(id(1)) A(id(2))]
  end
end
disp(idx)   % Linear index
[idx1,idx2]=ind2sub(size(A),idx);

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Lorenz 2013-6-11

编辑：Lorenz 2013-6-11

Ok Thanks. If I put m=8, matlab run into a very long loop (Busy), is that normal? In fact, there is one only point that the script can't associate with an adjacent point, because these other points are already chosen. It is not a big problem but that's a pitty. I'll try to correct it. please give me idea if you have. Thank you very much