[igraph] alpha.centrality() and evcent()

[santiago gil]

Hello all! Long time no post...

I have a question about the relationship between the functions alpha.centrality() and evcent(). According to my understanding of these two measures of centrality (which may very well be totally wrong) when e ("exo" in alpha.centrality) is 0 for all components or when alpha is very large, alpha centrality should reduce to eigenvector centrality. However, alpha.centrality() doesn't seem to work on undirected graphs, and evcent() doesn't seem to be affected by the directionality of the edges in directed graphs (the results are unchanged by transposing the adjacency matrix). The result of this is that in the implementations of these functions, exo=0 produces a singularity error, and the results for alpha.centrality() with alpha>20 and evcent() in my current problem show no resemblance whatsoever. Does anybody have any insight for me on this? Is it possible to calculate evcent() on directed graphs and measure the convergence of alpha.centrality() to evcent()? Or am I way off here?

Good wishes,

Santiago