Re: [igraph] issue with evcent

[Gábor Csárdi]

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 <address@hidden> wrote:
> Hi - for this tiny example graph, I am getting an eigenvector/value pair that 
> does not seem valid.
>
>> g<-read.graph("xxx",format="edgelist")
>> 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
>
>
>
>
>
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-- 
Gabor Csardi <address@hidden>     UNIL DGM