Re: [igraph] about ba.game

[Tamas Nepusz]

Hi,

Yes, there is a theoretical relation between the "power" parameter and the 
exponent of the fitted power law distribution. I think it is described in one 
of the original Barabasi papers about the model, not sure where and I don't 
have my reference list with me right now. However, this relation holds only for 
infinite networks -- for graphs with only a few thousand nodes, there is a 
significant finite size effect which may distort the "measured" exponent of the 
power law. The larger your networks are, the smaller the difference, but it is 
still there.

-- 
Tamas

On 2010.01.05., at 14:33, gunce orman 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) ???
> 
> 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??? 
> 
> Thank you very much
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