Looking for all sub-networks among a network

Dear All,

For a given network formed by lines and edges, how can I quickly find out all sub-networks? There is no connection among two sub-networks.

For example, the lines are given in a matrix A:

I know the sub-networks are: {6 2 3 4 5 7}, {1 8}. But how can I quickly find them out?

Thanks a lot. Benson

Answer 1

[Guillaume]

Please don't post screenshots, particularly as it's trivial to write your matrix as text in the question. We can't copy/paste screenshots into matlab.

It is trivial to find the number of components in a graph, using matlab's graph functions, in particular graph.conncomp:

A = [6 2
     6 3
     2 3
     4 5
     6 4
     1 8
     2 7]

g = graph(A(:, 1), A(:, 2));
max(conncomp(g))

[Benson Gou]

Guillaume,

Thanks for your response. What I want to obtain are the edge ID in each sub-network. For this example, I want to obtain the edges in each sub-network: sub1 = {6 2 3 4 5 7}; sub2 = {1 8}.

Thanks anyway.

[Guillaume]

You mean the node ID.

This is easily obtained with conncomp:

bin = conncomp(g);
accumarray(bin', (1:numel(bin))', [], @(nodes) {nodes'})