Re: [igraph] Working with large networks and how to sample from a graph?

[Gábor Csárdi]

On Wed, Apr 4, 2012 at 7:26 AM, Tamás Nepusz <address@hidden> wrote:
>> One idea I had was to take a small random sample from the network (say 5,000 
>> nodes) but I am not sure exactly how to do this in igraph.
>
> Well, it depends on how you want to do it. You can try selecting 5000 nodes 
> randomly from the entire network and then take the subgraph; this is 
> relatively simple:
>
> library(igraph)
> vs <- sample.int(vcount(g), 5000)-1
> g2 <- subgraph(g, vs)
>
> However, if your graph is large and sparse enough, there is a chance that the 
> resulting graph will not be connected at all, and then your estimates will 
> bear no resemblance at all to the "real" betweenness values.

Well, I'm not convinced that there is any kind of sampling that will
tell you much about betweenness values in the original network.
(Unless you network structure is special and you can use this fact in
the sampling.) I would recommend doing some simulations first, with
(say) snowball sampling.

Gabor

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-- 
Gabor Csardi <address@hidden>     MTA KFKI RMKI