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## RE: [igraph] issue with evcent

 From: Matthew Galati Subject: RE: [igraph] issue with evcent Date: Mon, 13 Apr 2009 14:54:02 -0400

```Why can't we have self-loops for eigenvector centrality?

For example, a valid eigenvector/value pair for this example could be:
vector = 0.8019,1,0.44504
value  = 1.80194

> -----Original Message-----
> Behalf Of Gábor Csárdi
> Sent: Monday, April 13, 2009 2:46 PM
> To: Help for igraph users
> Subject: Re: [igraph] issue with evcent
>
> Hi Matt,
>
> I am not sure that eigenvector centrality makes sense at all for
> graphs with self-loops. Maybe you just want to remove the self-loops
> with 'simplify()'.
>
> Best,
> Gabor
>
> On Mon, Apr 13, 2009 at 8:34 PM, Matthew Galati
> > Hi - for this tiny example graph, I am getting an eigenvector/value
> pair that does not seem valid.
> >
> >> gu<-as.undirected(g)
> >
> >> print.igraph(gu)
> > Vertices: 3
> > Edges: 3
> > Directed: FALSE
> > Edges:
> >
> > [0] 0 -- 1
> > [1] 0 -- 2
> > [2] 1 -- 1
> >
> >> evcent(gu)
> > \$vector
> > [1] 0.4811943 1.0000000 0.1939366
> >
> > \$value
> > [1] 2.481194
> >
> > The eigen pair is suppose to satisfy A.x=lambda.x
> >
> > But, in the second component, we have 1.48 != 2.48
> >
> > Note, I checked some other examples where there are no self-loops and
> they seem ok. So, the issue might be related to self-loops.
> >
> > Any ideas?
> >
> > Thanks,
> > Matt
> >
> >
> >
> >
> >
> > _______________________________________________
> > igraph-help mailing list
> > http://lists.nongnu.org/mailman/listinfo/igraph-help
> >
>
>
>
> --
> Gabor Csardi <address@hidden>     UNIL DGM
>
>
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