Re: [igraph] eigenvector centrality with second eigenvalue

[Yannick Rochat]

Dear Tamasz,

Thanks a lot for your answer. There is (at least) one thing I don't understand with arpack: what does "XX" mean in the "which attribute" ?

>  igraph.arpack.default

$bmat

[1] "I"

$n

[1] 0

$which

[1] "XX"

[…]

Best,

Yannick

PS.

Congratulations for the Springer book coming soon!

2014-05-24 23:21 GMT+02:00 Tamás Nepusz <address@hidden>:

> 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.