[igraph] Clustering coefficient vs. transitivity

[Jonathan F. Donges]

Dear Gabor and Tamas,

I'm using igraph 0.6 via the Python interface. From some test cases I
get the impression, that the function transitivity_undirected actually
gives the mean value of transitivity_local_undirected. Is this
correct?

This would imply that transitivity_undirected actually gives the
global clustering clustering coefficient as it is defined in equation
(2.10) in the Boccaletti review. In turn,
transitivity_local_undirected gives the local clustering coefficient,
as defined in equation (2.9) in this review paper. Most importantly,
this would imply that transitivity_undirected in fact does NOT give
the so called "transitivity", i.e., (3 x # of triangles in Graph) / (#
of connected triples of vertices in Graph) (equation (2.8) in
Boccaletti review).

It would be very helpful if you could clarify this! I know, its mainly
a matter of nomenclature, but both Newman and Boccaletti in their
reviews use "transitivity" in the sense of eq. (2.8).

Thank you very much,
Jonathan