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Re: [igraph] about ba.game
From: |
Gábor Csárdi |
Subject: |
Re: [igraph] about ba.game |
Date: |
Thu, 7 Jan 2010 12:46:15 +0100 |
Hi,
On Tue, Jan 5, 2010 at 2:33 PM, gunce orman <address@hidden> wrote:
> Hello,
>
> I use ba.game funciton to create a scale free network. And then I'm trying
> to calculate the exponent of power law for the different value of the
> parameter "power" of ba.game... Is there any explication of the relation
> between that power parameter ( the alpha exponent of the choosing the
> vertices) and the gamma ( the exponent of the power low of the degrees) ???
the degree distribution is a power law only if the "power" parameter
is one. Otherwise it will be exponential. See e.g.
http://arxiv.org/abs/cond-mat/0005139
> If i'm not wrong, for power=1, normally gamma must be 3, because it is
> linear preferential attachement. But when I produce a set of network for
> power=1 and try to find their gamma values by using power.low.fit(), I have
> many different values than 3... Am I doing something wrong???
Tamás mentioned the finite size effect. Another thing is that ba.game
is a bit different from the model that was proven to lead to gamma=3,
e.g. ba.game does not generate loop edges. See
http://www3.interscience.wiley.com/journal/79502716/abstract
Gabor
> Thank you very much
>
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>
--
Gabor Csardi <address@hidden> UNIL DGM