[igraph] Question about finding power in a scale-free graph

[Narges Zarabi]

Dear all,

With the following command, I am generating a graph according to Barabasi-model, which gives me a network with 100000 nodes and preferential attachment or power =1

g <- barabasi.game(100000 ,power=1)

But when I try to find the power by fitting to the power-law (which is the degree distribution) using following command:

d <- degree(g, mode="in")

dd <- degree.distribution(g, mode="in", cumulative=TRUE)

alpha <- power.law.fit(d, xmin=20)

I get an alpha = 2.8 , which is different from the power I used in building the graph. Does anyone have any explanation for this? Many thanks in advance

Regards, Narsis