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Re: [igraph] about ba.game

From: Tamas Nepusz
Subject: Re: [igraph] about ba.game
Date: Tue, 5 Jan 2010 20:50:08 +0100


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.


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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