function C = clusttriang(A)
% CLUSTTRIANG computes clustering coefficient based on number of triangles
% C = CLUSTTRIANG(A) compute the clustering coefficient C of the
% adjacency matrix A, based on the ratio (number of triangles)/(number of triples).
% (1)This is a subtly different definition than that of Watts & Strogatz (1998).
% In the present form, it does give the fraction of neighbouring nodes
% that are also neighbours of each other. (Also note: for directed
% graphs, this means *any* direction of connection, as along as all three
% nodes are connected).
% (2) This function uses the method of Keeling (1999) to compute C.
% Mark Humphries 22/8/2006
A2 = A * A;
A3 = A2 * A;
sumA2 = sum(sum(A2));
C = trace(A3) / (sumA2 - trace(A2));