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 <[email protected]>: > > 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. >
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