[igraph] betweenness centrality for weighted graphs

[T.O. Richardson]

Hi List,
Please see correspondence below for the calculation of weighted betweenness 
in igraph.


On Tue, Mar 29, 2011 at 9:11 AM, T.O. Richardson
<address@hidden> wrote:
> Hi Gábor & Tamas,
> I have a query about igraph in R.
> I have a dynamic undirected weighted graph and would like to calculate the
> betweenness centrality for each vertex at each time-point.
> However, the betweenness function in igraph version 0.5.5-2 does not seem 
to
> take into account the edge weights.
>
> My code is:
> actors <- data.frame(name=ants))
> relations <- data.frame(from=fromm, to=too )
> net <-graph.data.frame(relations, directed=FALSE, vertices=actors)
> E(net)$weight <- weights
> betweenness(net, V(net), directed=FALSE)
>
> The resulting betweenness from the above is identical irrespective of
> whether you add the weights to the edges, or not.
>
> I looked at the CRAN changelog, where it states (i think) that the file
> "interfaces/R/igraph/R/structural.properties.R" has been modified (on
> 2009-08-02 14:04:01) to include edge weighting.
> If I try to simply cut & paste the code (that should take weights into
> account) for the betweenness function from the CRAN change-log (see 
below),
> then I get the error 'could not find function "as.igraph.vs" ' . I can't
> interpret the C code in the changelog, so i am abit lost..
>
> Many Thanks,
> Tom Richardson
>
>
> ## code from the CRAN igraph change-log:
> betweenness <- function(graph, v=V(graph), directed=TRUE, weights=NULL,
>                       verbose=igraph.par("verbose")) {
>                       nobigint=TRUE, 
verbose=igraph.par("verbose")) {
>  if (!is.igraph(graph)) {
>    stop("Not a graph object")
>  }
>  on.exit( .Call("R_igraph_finalizer", PACKAGE="igraph") )
>  .Call("R_igraph_betweenness", graph, as.igraph.vs(graph, v),
>       as.logical(directed), weights, as.logical(verbose),
>       as.logical(directed), weights, as.logical(nobigint),
>       as.logical(verbose),
>        PACKAGE="igraph")
> }




Dear Tom,

please send these kind of questions to the igraph-help mailing list,
see http://igraph.sf.net. Thanks!

As for your question, indeed, weighted betweenness is only implemented
in the 0.6 development version. Copying the R code from 0.6 does not
help, because the implementation is in C.

You can download the 0.6 version from
http://code.google.com/p/igraph/downloads/list
Go for igraph_nightly_0.6-2410-20110328.tar.gz, because the newest
version does not work properly.
This is an R source package, which works on Linux or OSX (if you can
compile C/C++ programs on OSX). If you need a windows package, then I
can send you one.

Best,
Gabor