[igraph] Generating scale-free networks with different exponents

[Narges Zarrabi]

Hi,

I am using the following code to generate scale-free networks with different exponents, taken from (http://127.0.0.1:20410/library/igraph/html/degree.sequence.game.html).

n<-1000

scale<-1.9

degs <- sample(1:n, n, replace=TRUE, prob=(1:n)^(-scale))

if (sum(degs) %% 2 != 0) { degs[1] <- degs[1] + 1 }

g <- degree.sequence.game(degs, method="vl")

all(degree(g) == degs)

The code works sometimes, but most of the times I receive the following error:

Error in degree.sequence.game(degs, method = "vl") : 

  At gengraph_mr-connected.cpp:139 : Cannot realize the given degree sequence as an undirected, simple graph, Invalid value

Also I don't understand what is the reason having the last line in the code: all(degree(g) == degs)

Any comments that can help? Many thanks

Narcis