% This function outputs the adjacency matrix of a subgraph given the
% supergraph and the node set of the subgraph
% INPUTs: adj - supergraph adjacency matrix, S - vector of subgraph node indices
% OUTPUTs: adj_sub - adjacency matrix of the subgraph 
% GB, January 5, 2006

function adj_sub = subgraph(adj,S)

adj_sub = adj(S,S);