gephi/trunk — Issue #57: Directed Graph cluster coefficient provides incorrect values in certain situations
Author: mbastian
Created: 2011-10-22 16:42:00+00:00
State: open
Labels: clustering, coefficient, Confirmed, digraph, High

Hi,

I have observed that the cluster coefficient statistics for digraphs appear to be incorrect in certain situations.

For example the following graph is reported to have a cluster coefficient of 0.833 (which I believe is correct):
a->b
b->c
c->b
a->c
c->a

The following graph which is equivalent to the above graph (they both represent a triangle minus one directed edge) is incorrectly report to have a coefficient of 0.667:
a->b
b->a
b->c
c->b
a->c

I believe that the problem stems from the fact that the clustering analysis incorrectly reports the local clustering coefficient of a as 0.5 rather 1! Perhaps there is a bug in the local clustering coefficient code?

I have provided the example digraphs as dot files for you to repeat the error should that be helpful.

This bug may need an urgent fix as the statistics produced by the clustering coefficient code for directed graphs may be erroneous?