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Re: [igraph] Alpha Centrality Function Crashes

From: Gabor Csardi
Subject: Re: [igraph] Alpha Centrality Function Crashes
Date: Thu, 24 Apr 2008 18:04:29 +0200
User-agent: Mutt/1.5.13 (2006-08-11)


I get

> g <- erdos.renyi.game(40000, 90000, type="gnm")
> alpha.centrality(g)
Error in get.adjacency(graph) : 
  At vector.pmt:408 : cannot reserve space for vector, Out of memory

Yes, this function uses an adjacency matrix, so you cannot use it
on such a big graph. You can try the 'Matrix' package. 
See the code of 'alpha.centrality', get the edge list of 
the graph with 'get.edgelist', convert it to a (sparse) Matrix,
and solve the equation with the sparse matrix solver.
It should not be too difficult, i can help you if you need help.


On Thu, Apr 24, 2008 at 08:37:10AM -0700, Judd Antin wrote:
> Hi all,
> I've been using igraph in R to look at a a very large, sparse directed 
> network of about 58,000 nodes and 87,000 edges. I am interested in 
> calculating alpha centrality scores, but the alpha.centrality function 
> crashes R for me instantaneously. I've tried this on both Windows and 
> Mac builds of the library (in case of a platform dependent issue), with 
> the same results.
> Does anyone have any insight on how I could get this to work? Is the 
> size of the network simply too large? I also noticed in the manual that 
> 'singular adjacency matrices' can cause problems for the algorithm, but 
> I'm not sure what a 'singular adjacency matrix' is.
> Any advice appreciated.
> Thanks!
> --Judd
> --
> Judd Antin
> School of Information
> University of California Berkeley
> address@hidden
> web: http://technotaste.com
> blog: http://technotaste.com/blog
> _______________________________________________
> igraph-help mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/igraph-help

Csardi Gabor <address@hidden>    UNIL DGM

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