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Re: [igraph] Alpha Centrality Function Crashes

From: Judd Antin
Subject: Re: [igraph] Alpha Centrality Function Crashes
Date: Thu, 24 Apr 2008 16:15:05 -0700
User-agent: Thunderbird (Windows/20080213)


Thanks for the suggestion. That may be a little beyond my abilities. It's easy enough for me to get an edgelist, and I can see roughly which equation I'll need to solve. However, I'm not sure of how to coerce the edgelist into a sparse matrix, nor how exactly to use the sparse matrix solver.

Any help is greatly appreciated!


Gabor Csardi wrote:
I get

g <- erdos.renyi.game(40000, 90000, type="gnm")
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.



Judd Antin
School of Information
University of California Berkeley
web: http://technotaste.com
blog: http://technotaste.com/blog

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