How to count the number of occurrences of each pair in a cell?

Question

Md Shahidullah Kawsar 2018-10-30

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/427004-how-to-count-the-number-of-occurrences-of-each-pair-in-a-cell

编辑： Akira Agata 2018-10-31

Suppose I have a cell array

C = {[1; 2; 3]; [1; 2; 3; 4]; [1; 2]};
c{:}
ans = 
1
2
3
ans =
1
2
3
4
ans=
1
2
 % where any digit won't repeat in the individual cell.

I need to find out the number of occurrences of each pair. Expected output:

Pair(1,2) = 3 occurences; 
Pair(1,3) = 0;
Pair(1,4) = 0;
Pair(2,1) = 0;
Pair(2,3) = 2;
Pair(2,4) = 0;
Pair(3,1) = 0;
Pair(3,2) = 0;
Pair(3,4) = 1;

How can I find it?

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Rik 2018-10-30

What code have you tried so far? It looks like there is a simple, naive approach with some loops that would solve it (not sure if there are some tricks you can pull to speed it up substantially).

Md Shahidullah Kawsar 2018-10-31

编辑：Md Shahidullah Kawsar 2018-10-31

在 MATLAB Online 中打开

I was trying this code for the array A = [1 2 3; 2 3 1; 2 1 3]

      for n = 2:3
      [j,i]=ind2sub(fliplr(size(A)),  strfind(reshape(A.',1,[]),[1 n]).');
      C = [i,j];
      d = numel(C(j));
      T9 = table(1, n, d)
      end

but it has 2 problems: (1) error occurs when the second row ends with 1 and the third row begins with 2. (2) for cell array, this code doesn't work

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Answer 1

Akira Agata 2018-10-31

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https://ww2.mathworks.cn/matlabcentral/answers/427004-how-to-count-the-number-of-occurrences-of-each-pair-in-a-cell#answer_344284

编辑：Akira Agata 2018-10-31

在 MATLAB Online 中打开

I think one possible way would be like this:

c = {[1; 2; 3]; [1; 2; 3; 4]; [1; 2]};
Pair = [repelem((1:4)',4,1),repmat((1:4)',4,1)];
Count = zeros(size(allPair,1),1);
for kk = 1:numel(c)
  d = [c{kk}(1:end-1),c{kk}(2:end)];
  [~,lo] = ismember(d,Pair,'rows');
  Count = Count + (histcounts(lo,1:size(Pair,1)+1))';
end
T = table(Pair,Count);

The output is:

>> T
T =
16×2 table
   Pair     Count
  ______    _____
  1      0  
  2      3  
  3      0  
  4      0  
  1      0  
  2      0  
  3      2  
  4      0  
  1      0  
  2      0  
  3      0  
  4      1  
  1      0  
  2      0  
  3      0  
  4      0