[R-sig-networks] Calculating Betweenness - Efficiency Problem

[Senthil Purushothaman]

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