Hi, I believe that this is an overflow error in the C core that was fixed (by Tamas, actually :) in the development tree, but it is still there in your version: http://bazaar.launchpad.net/~igraph/igraph/0.6-main/revision/2897
Thanks for the report! Best, Gabor On Tue, Jan 29, 2013 at 5:09 PM, Tamás Nepusz <[email protected]> wrote: > Hi, > > Thanks for the bug report. It seems that the C core of igraph does not > have this error so the problem is in the glue code that bridges the gap > between the C core and R itself. Gabor will probably fix it soon (if it is > not fixed already in the development tree). In the meanwhile, you can work > around the bug by knowing that the theoretical maximum of > centralization.betweenness is (n-1)*(n-1)*(n-2) if your graph is directed > and has n vertices, and (n-1)*(n-1)*(n-2)/2 if it is undirected. > > All the best, > Tamas > > On 29 Jan 2013, at 19:47, F Witmer <[email protected]> wrote: > > > I searched the archives and see some prior discussion regarding a > problem with the betweenness calculation, but it looks like those issues > were resolved. When calculating the betweenness centralization, the > theoretical max value appears to be incorrect causing nonsensical > (negative) results. Here's some R code and the results I get to reproduce > it: > > > > > library("igraph") > > > g <- barabasi.game(5000) > > > centralization.betweenness(g)$theoretical_max > > [1] 345973414 > > > centralization.betweenness(g)$centralization > > [1] 0.07282635 > > > g <- barabasi.game(10000) > > > centralization.betweenness(g)$theoretical_max > > [1] -1127329970 > > > centralization.betweenness(g)$centralization > > [1] -0.02273176 > > > > And here's my session info: > > > > > sessionInfo() > > R version 2.15.2 (2012-10-26) > > Platform: x86_64-w64-mingw32/x64 (64-bit) > > > > locale: > > [1] LC_COLLATE=English_United States.1252 LC_CTYPE=English_United > States.1252 > > [3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C > > [5] LC_TIME=English_United States.1252 > > > > attached base packages: > > [1] stats graphics grDevices utils datasets methods base > > > > other attached packages: > > [1] igraph_0.6-3 > > > > loaded via a namespace (and not attached): > > [1] tools_2.15.2 > > > > > > _______________________________________________ > > igraph-help mailing list > > [email protected] > > https://lists.nongnu.org/mailman/listinfo/igraph-help > > > _______________________________________________ > igraph-help mailing list > [email protected] > https://lists.nongnu.org/mailman/listinfo/igraph-help > -- Gabor Csardi <[email protected]> MTA KFKI RMKI
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