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## Re: [igraph] problems with parameters in barabasi.game()

 From: Csardi Gabor Subject: Re: [igraph] problems with parameters in barabasi.game() Date: Wed, 10 Sep 2008 16:40:30 +0200 User-agent: Mutt/1.5.9i

```On Wed, Sep 10, 2008 at 04:22:19PM +0200, Mario Lavezzi wrote:
> Hello Gabor
> thank you so much.
>
> I think I got confused by the different notation used in the papers I am
> considering at the moment.
> >It is still not the formula in the Dorogovtsev paper, though. I don't
> >know why, maybe they don't consider multiple edges, or the results are
> >only valid in some limit.
> >
> I think that things are a little different because, they actually allow
> multiple (directed) links, consider a parameter of "attractiveness" of a
> node which is only initial (and so it is not used at each time step as
> the "zero.appeal" value, as I understand).
>
> One last question: can you suggest a quick way of generating degree
> sequences with a given power-law exponent to  be used  in  the
> "degree.sequence.game"?

Mario, I would try 'sample' first, e.g.

degs <- sample(1:1000, 1000, replace=TRUE, prob=(1:1000)^-2)
g <- degree.sequence.game(degs, method="vl")

Note that it is not always possible to realize a given degree sequence,
e.g. if the sum of degrees is odd, then it is trivially impossible.

G.

> >If you just want to have graphs with various power law degree
> >distributions,
> >you might consider using 'degree.sequence.game', with method="vl", here
> >you can prescribe the exact degree distribution. It always generated
> >connected graphs, but probably this is not a problem.
> >
> >
> Thanks a lot!
> best,
> Mario
>

--
Csardi Gabor <address@hidden>    MTA RMKI, ELTE TTK

```