MATLAB: Weighted matrix to edge list

edgesmatrix

Hello,
Is there a quick way to transform a matrix such as
[10 1 9; 1 5 4; 2 1 5]
into an edge list with the information containing both i and j (also when i=j) and the value of the pair. For example
[1 1 10; 1 2 1; 1 3 9; 2 1 1; 2 2 5; 2 3 4; 3 1 2; 3 2 1; 3 3 5].
Thanks in advance for any help.

Best Answer

One way based around ndgrid:
>> M = [10 1 9; 1 5 4; 2 1 5];
>> N = M.';
>> S = size(N);
>> [R,C] = ndgrid(1:S(1),1:S(2));
>> [C(:),R(:),N(:)]
ans =
    1    1   10
    1    2    1
    1    3    9
    2    1    1
    2    2    5
    2    3    4
    3    1    2
    3    2    1
    3    3    5
If the order is not important then you do not need the transpose. Note that in MATLAB the first dimension is down the columns.
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