Re: [igraph] Something strange about the Power-law distribution of Barabasi.game

[Gábor Csárdi]

Hi Ravi,

I don't know.

What the generator does, is that it uses a big bag of vertex ids,
where each id might appear multiply times (This is a multiset in more
mathematical terms.) In each time step, each vertex id appears in the
bag exactly as many times as its in-degree, plus once more. (The
latter is to allow zero in-degree vertices to get incoming edges.)
When edges are created, we just choose elements from the bag. A side
effect of this algorithm is that it might create multiple edges.

Best,
Gabor

On Sat, May 1, 2010 at 1:00 AM, Ravi Varadhan <address@hidden> wrote:
> Hi All,
>
>
>
> We have been trying to understand the degree distribution of the network
> generated by the Barabasi game, using the barabasi.game(), function in
> “igraph”.  We are noticing some strange behavior of the degree distribution
> near the right tail (i.e. large values of degree).  In this region, the
> degree distribution appears to significantly deviate from a power law
> distribution.  Is there something wrong with the code for Barabasi game or
> is this the expected behavior?
>
>
>
> Here is the code that demonstrates this problem:
>
>
>
> g <- barabasi.game(100000)
>
>
>
> d <- degree(g, mode="in")
>
>
>
> ans <- table(d)
>
>
>
> # the folowing plot doesn't look nice in the right-tail region
>
> plot(as.numeric(names(ans))+ 1, table(d), log="xy")
>
>
>
>
>
> Thanks for any insights.
>
>
>
> Best regards,
>
> Ravi.
>
>
>
> ----------------------------------------------------------------------------------------------------------
>
> Ravi Varadhan, Ph.D.
>
> Assistant Professor,
>
> Center on Aging and Health,
>
> Johns Hopkins University School of Medicine
>
> (410)502-2619
>
> address@hidden
>
> http://www.jhsph.edu/agingandhealth/People/Faculty_personal_pages/Varadhan.html
>
>
>
>
>
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>
>



-- 
Gabor Csardi <address@hidden>     UNIL DGM