[R] Calculating Betweenness - Efficiency problem

[Gabor Csardi]

Senthil,

you can try the 'igraph' package. Export your two-column Excel file
as a .csv, use 'read.csv' to read that into R, then 'graph.data.frame'
to create an igraph graph from it. Finally, call 'betweenness' on 
the graph. It is really just three/four lines, something like this:

tab <- read.csv(...)
g <- graph.data.frame(tab)
bet <- betweenness(g)
bet <- data.frame(city=V(g)$name, betweenness=bet)

The last line creates a two column data frame with the betweenness 
score of each city. 

Best,
Gabor

On Sat, Jul 19, 2008 at 02:59:07PM -0700, Senthil Purushothaman wrote:
> Hi Jim,
>     Thank you for the response. Your suggestion will help me avoid the whole text to number conversion process that I perform using LookUp in excel. I will definitely give it a shot. But it still doesn't address the vector conversion since a graph file is drawn only using the vectors. Assuming that I use 'factor' to convert the characters to numbers, how do I convert these numbers into vectors?
> 
> Thanks,
> Senthil
> 
> 
> 
> 
> -----Original Message-----
> From: jim holtman [mailto:jholtman at gmail.com]
> Sent: Sat 7/19/2008 4:49 AM
> To: Senthil Purushothaman
> Cc: r-help at r-project.org
> Subject: Re: [R] Calculating Betweenness - Efficiency problem
>  
> It would seem that you can output the initial file from EXCEL, read it
> into R with 'read.csv' and then use 'factor' to convert the characters
> for City1 and City2 to the numbers that you want to use.  Have you
> tried this approach?
> 
> On Fri, Jul 18, 2008 at 3:51 PM, Senthil Purushothaman
> <spurushothaman at lnxresearch.com> wrote:
> > Hello,
> >
> > I am calculating 'Betweenness' of a large network using R. Currently, I have the node-node information (City1-City2) in an excel file, present in two columns where column A has City1 and column B has City2 that city1 is connected to. These are the steps that I go through to calculate betweenness of my network.
> >
> > a) Convert the City1-City2 (text) into Number1-Number2 in the excel file where every unique city has a unique number.
> > b) Paste all the city-city information separated by comma into c(...) in the R GUI to obtain the corresponding vectors. As you can imagine this copy-paste operation takes a long time. Example: c(1,3,1,5,2,4,2,5). Just fyi, I have a text file that contains all nodes separated by comma based on the appropriate link information.
> > c) Then, I create a graph file with the above vector.
> > d) I use the graph file to calculate betweenness of my network.
> >
> > I am sure there must be a better, more efficient way to calculate betweenness. Ideally, I would like to just have the City1 - City2 (link) information in two columns in an excel file and calculate the betweenness from that file directly.
> >
> > Please provide an optimal solution for this problem. I appreciate your time and help.
> >
> > Thanks,
> > Senthil
> >
> >        [[alternative HTML version deleted]]
> >
> > ______________________________________________
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> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
> 
> 
> 
> -- 
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
> 
> What is the problem you are trying to solve?
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

-- 
Csardi Gabor <csardi at rmki.kfki.hu>    UNIL DGM