IncidenceMatrix(G) returns the incidence matrix of a graph G whose rows are indexed by the vertices and columns by the edges of G.  The order of the edges is defined by Edges(G).

If G is undirected the entry  of this -matrix is  iff vertex i is incident to edge j.

If G is directed the entry  of this -matrix is  iff vertex i is the head of arc j and  iff vertex i is the tail of arc j.

If G is directed and reverse is specified, the entry  of this -matrix is  iff vertex i is the head of arc j and  iff vertex i is the tail of arc j.