Hi Jan, > Unfortunately I can't find any scientific reference how such a cutoff > influences the validity of the results. Are there any such references > available? Or any rules of thumb? Unfortunately I am not aware of any such references -- to be honest, the cutoff option was introduced only as kind of "quick hack" to allow a rudimentary form of estimation. NetworkX seems to implement a different estimation method for betweenness:
http://networkx.lanl.gov/reference/generated/networkx.algorithms.centrality.betweenness_centrality.html The method that NetworkX uses involves taking a random sample of the nodes in the network and then calculating shortest paths from these nodes only to all the other nodes. The size of the sample then determines the precision of the approximation. The idea is outlined in this paper: http://www.inf.uni-konstanz.de/algo/publications/bp-celn-06.pdf Other references that might prove to be relevant: http://www.cc.gatech.edu/~mihail/WAW07.pdf http://cs.brown.edu/~matteo/papers/RiondatoKornarop-BetweennessSampling.pdf Another solution that you might use is to calculate and log the shortest paths from different source nodes into separate files, using separate igraph processes, and then accumulate the shortest paths in a post-processing stage to obtain the actual betweenness scores. This method is useful if you have access to one or more computers with many CPU cores as each CPU core can then be responsible for processing a different source node, and the computations can run in parallel. (igraph is single-threaded by nature, so it will use only a single CPU core for betweenness calculation, even if you have more than one core). All the best, -- T. _______________________________________________ igraph-help mailing list [email protected] https://lists.nongnu.org/mailman/listinfo/igraph-help
