Hi, evcent is not very good with unconnected graphs, it is better to decompose your graph into connected components.
Probably there should be a warning for this. Gabor On Thu, May 23, 2013 at 1:58 PM, Florian Umlauf <[email protected]>wrote: > Hi, > > I was wondering how the following result could happen. I am using > igraph::evcent for the calculation for my own model statistics. So I make > some experiments and repeat some statistics. > > > a <- igraph::graph.ring(10) + igraph::graph.ring(10) > > igraph::evcent(a,scale=FALSE)$vector > [1] 0.2236051 0.2236051 0.2236051 0.2236051 0.2236051 0.2236051 0.2236051 > [8] 0.2236051 0.2236051 0.2236051 0.2236084 0.2236084 0.2236084 0.2236084 > [15] 0.2236084 0.2236084 0.2236084 0.2236084 0.2236084 0.2236084 > > > a <- igraph::graph.ring(10) + igraph::graph.ring(10) > > igraph::evcent(a,scale=FALSE)$vector > [1] 0.2236066 0.2236066 0.2236066 0.2236066 0.2236066 0.2236066 0.2236066 > [8] 0.2236066 0.2236066 0.2236066 0.2236070 0.2236070 0.2236070 0.2236070 > [15] 0.2236070 0.2236070 0.2236070 0.2236070 0.2236070 0.2236070 > > > a <- igraph::graph.ring(10) + igraph::graph.ring(10) > > igraph::evcent(a,scale=FALSE)$vector > * [1] 0.0000000 0.0000000 0.0000000 0.0000000 0.0000000 0.0000000 > 0.0000000** > ** [8] 0.0000000 0.0000000 0.0000000* 0.2236073 0.2236073 0.2236073 > 0.2236073 > [15] 0.2236073 0.2236073 0.2236073 0.2236073 0.2236073 0.2236073 > > > As you can see I get in return different values (zeros) at the third try. > There are some zero values How could that happen? It also happens with > scale=TRUE. > > > a <- igraph::graph.ring(10) + igraph::graph.ring(10) > > igraph::evcent(a)$vector > [1] 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 > > > a <- igraph::graph.ring(10) + igraph::graph.ring(10) > > igraph::evcent(a)$vector > [1] 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 > > > a <- igraph::graph.ring(10) + igraph::graph.ring(10) > > igraph::evcent(a)$vector > [1] 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 > > > a <- igraph::graph.ring(10) + igraph::graph.ring(10) > > igraph::evcent(a)$vector > [1] 0.9999876 0.9999876 0.9999876 0.9999876 0.9999876 0.9999876 0.9999876 > [8] 0.9999876 0.9999876 0.9999876 1.0000000 1.0000000 1.0000000 1.0000000 > [15] 1.0000000 1.0000000 1.0000000 1.0000000 1.0000000 1.0000000 > > Thank you for answers. > > R version 3.0.1 (2013-05-16) > Platform: x86_64-w64-mingw32/x64 (64-bit) > > locale: > [1] LC_COLLATE=German_Germany.1252 LC_CTYPE=German_Germany.1252 > [3] LC_MONETARY=German_Germany.1252 LC_NUMERIC=C > [5] LC_TIME=German_Germany.1252 > > attached base packages: > [1] stats graphics grDevices utils datasets methods base > > loaded via a namespace (and not attached): > [1] igraph_0.6.5-1 > > > _______________________________________________ > 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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