Creating adjacency matrix from 4x6 matrix

Question

I have a 4x6 matrix (directed network) similar to the following example:So first column represent individuals and each rows represent individual friendship with other individuals so first row represent individual 1 friendship with 2 and 5 and similarly row 3 represent individual 5 friendship with individuals 2 and 6. Zeros have no meaning.

[ 1 2 0 5 0 0; 
  2 1 0 0 5 6; 
  5 2 6 0 0 0; 
  6 1 2 0 0 5; ]

So now since there are four individuals I want **4x4 adjacency matrix representing friendship meaning 0 indicating no friendship and 1 indicating friendship**. So first row in the following represent individual 1 friendship with 2,5 as 1 meaning they are friend and 0 for 6 they are not friend. Similarly row two represent friendship individual 2 with 1,5 and 6 as 1 meaning he/she is friend with all the individuals.

[ 0 1 1 0; 
  1 0 1 1;  
  0 1 0 1; 
  1 1 1 0; ]

So how can I get this matrix in MATLAB?

Answer 1

The most straightforward approach is to modify the answer found here:

A = [1 2 0 5 0 0; 
     2 1 0 0 5 6; 
     5 2 6 0 0 0; 
     6 1 2 0 0 5];

adjMat = zeros(max(A(:)));   % create full 6x6 matrix, then chop it down
for ind = 1:size(A,1)
    % Flag 1 on each row 'ind' at the indices mentioned in col 2-5
    adjMat(A(ind,1), nonzeros(A(ind,2:end))) = 1;
end
% use only rows/columns with indices in first column of A
adjMat = adjMat(A(:,1), A(:,1));

If it turns out you want to use the full 6x6 matrix, just stop before the last line or use the 6x6 input matrix with zeros in the unwanted rows (in which case the last line is again unnecessary).