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## Re: [igraph] Generating scale-free networks with different exponents

**From**: |
Gábor Csárdi |

**Subject**: |
Re: [igraph] Generating scale-free networks with different exponents |

**Date**: |
Tue, 8 Nov 2011 11:06:57 -0500 |

On Tue, Nov 8, 2011 at 10:44 AM, Narges Zarrabi <address@hidden> wrote:
>* 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*
Depending on your exponent, it is possible that the generated degree
sequence cannot be realized as a graph. Practical solution: just
continue generating graphs until you have enough and ignore the
errors. (See ?try for ignoring the errors.)
>* Also I don't understand what is the reason having the last line in the*
>* code: all(degree(g) == degs)*
It's a check to show you that the generated graph indeed has the
prescribed degree sequence.
Best,
Gabor
>* Any comments that can help? Many thanks*
>* Narcis*
>* _______________________________________________*
>* igraph-help mailing list*
>* address@hidden*
>* https://lists.nongnu.org/mailman/listinfo/igraph-help*
>
>
--
Gabor Csardi <address@hidden> MTA KFKI RMKI