How to compare each element of an array with the rest of the elements for several rows independently?
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Mohammad Fazelpour
on 13 Apr 2019
Commented: Stephen23
on 17 Apr 2019
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;
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Accepted Answer
Stephen23
on 13 Apr 2019
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:
2 Comments
Stephen23
on 17 Apr 2019
>> 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
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