How to compare each element of an array with the rest of the elements for several rows independently?

I want to compare each element of an array with the rest of the elements (in a single row of a matrix) and identify which pair(s) of indexes have both values of 1 (in each row). 'nchoosek' works for one row, but when other rows are added like the following example, the code does not work. It is expected the results of each row is independent of other rows.

A =[1 1 0 1 1 0; 0 0 1 0 0 1; 0 0 0 1 1 1; 1 1 1 1 1 1];
for i=1:4
index_matrix(i,:,:) = nchoosek(find(A(i,:)==1),2)
end;                                                                                                      

[madhan ravi]

Explicitly show how your output should look like.

Answer 1

[Stephen23]

Because each array has a different size you will have to use a cell array:

A = [1 1,0,1,1,0;0,0,1,0,0,1;0,0,0,1,1,1;1,1,1,1,1,1];
N = size(A,1);
C = cell(1,N);
for k = 1:N
    V = find(A(k,:));
    C{k} = nchoosek(V,2);
end

giving:

>> C{:}
ans =
     1     2
     1     4
     1     5
     2     4
     2     5
     4     5
ans =
     3     6
ans =
     4     5
     4     6
     5     6
ans =
     1     2
     1     3
     1     4
     1     5
     1     6
     2     3
     2     4
     2     5
     2     6
     3     4
     3     5
     3     6
     4     5
     4     6
     5     6
>> 

See also:

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html

[Mohammad Fazelpour]

Now, I want to access the cell array, C, and identify how many times different indexes have occurred. For example, in the case of above example, the output would be

Cell Array # of times

1 2 2

1 3 1

1 4 2

......

5 6 2

I wrote this

[row, column] = size(C)

for i=1:4

Sum (i) = cellfun(@(x) find(x=='1 2'), C);

end

which is not correct. Your help is appreciated.

[Stephen23]

>> M = vertcat(C{:});
>> [U,~,X] = unique(M,'rows');
>> N = histc(X,1:max(X));
>> [U,N]
ans =
   1   2   2
   1   3   1
   1   4   2
   1   5   2
   1   6   1
   2   3   1
   2   4   2
   2   5   2
   2   6   1
   3   4   1
   3   5   1
   3   6   2
   4   5   3
   4   6   2
   5   6   2