Re: [igraph] eigenvector centrality with second eigenvalue

[Tamás Nepusz]

> Is there an option with evcent (or ARPACK) that allows to get the
> eigenvector (centrality) associated to the 2nd or further eigenvalue
> inside igraph ? You notice in the help file that the largest cliques
> may pull the highest values.
The R interface of igraph contains a direct interface to ARPACK so you can use 
it to calculate the eigenvector corresponding to the second eigenvalue of the 
adjacency matrix. However, note that it is not guaranteed that the eigenvector 
corresponding to the second (or any other but the first) eigenvalue contains 
positive entries only, in which case the interpretation of the entries of the 
vector as centrality scores is a bit problematic (IMHO).

Best,
T.