vlt.graph.mergegraph

  MERGEGRAPH - merge adjacency matrixes of 2 graphs

  [MERGED_GRAPH, INDEXES, NUMNEWNODES] = vlt.graph.mergegraph(G1, G2, NODENUMBERS2_1)

  Creates a merged graph from two overlapping adjacency matrixes
  G1 and G2. G#(i,j) is the weight of the connection from node
  i to j for each graph. NODENUMBERS2_1 are the node index values
  of the nodes of G2 in G1. If any entries of NODENUMBERS2_1 are
  greater than the number of nodes of G1, then they are assumed to
  be nodes that are not present in G1, but they will be added in the
  new graph.

  INDEXES is a structure array of the entries that make up the new
  panels of the merged adjacency matrix MERGED_GRAPH. The fields
  'upper_right', 'lower_left', and 'lower_right' have the index values
  of G2 that are taken to fill out the graph. For 'lower_right', the
  matrix is square and full, and the index values are the locations in
  G2. For 'lower_left' and 'upper_right', the matrixes may be sparse
  if there are nodes in G1 that are not in G2. So the index values
  have two fields: 'merged' (the index values of the panel in the merged
  matrix) and 'G2' (the corresponding index values in G2). 

  Any connection that is 'open' will have weight Inf.

  Note that in performing this merge, the connections among the nodes of
  G1 are NOT modified. So this function is not a means of providing additional
  information about the connectivity of those nodes.

  See also: DIGRAPH

  Example: 
             G1 = [ 1 1 1 ; 0 1 0; 0 0 1 ]; 
             G2 = [ 1 1 ; 0 1 ];
             nodenumbers2_1 = [ 1 4 ];
             [G3,indexes,numnewnodes] = vlt.graph.mergegraph(G1,G2,nodenumbers2_1);
             lower_right = G2(indexes.lower_right);
             lower_left = inf(numnewnodes,size(G1,1));
             upper_right = inf(size(G1,1),numnewnodes);
             lower_left(indexes.lower_left.merged) = G2(indexes.lower_left.G2);
             upper_right(indexes.upper_right.merged) = G2(indexes.upper_right.G2);
             G4 = [ G1 upper_right; lower_left lower_right ];
             G3==G4 % it does