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Re: [igraph] cohesive.blocks: exporting blocks as a data frame

From: joe j
Subject: Re: [igraph] cohesive.blocks: exporting blocks as a data frame
Date: Sat, 14 May 2011 09:53:44 +0200

Thank you very much Gábor for the quick solution and for the
clarifications. I hope to hear if you make any changes to the code in
the future.

On Fri, May 13, 2011 at 8:03 PM, Gábor Csárdi <address@hidden> wrote:
> Dear Joe,
> On Fri, May 13, 2011 at 6:28 AM, joe j <address@hidden> wrote:
>> Dear all,
>> Using igraph version .6 in R 2.12.2, I am trying to calculate cohesive
>> blocks for each year over a period of time. For later analysis I need
>> a matrix (that's a data frame which can be exported, for example as a
>> csv or dta file) with the following minimum information: vertex name,
>> block code (to identify the block), and hierarchy level. This way, I
>> hope, among other things, to keep track of the pattern of block
>> membership of each vertex over time. Knowledge of hierarchy level
>> would enable me to combine several blocks in order to have smaller
>> number of blocks. Would this be possible? I tried exporting the data
>> to pajek, but couldn't figure out a way to extract the information I
>> needed. Any suggestion would be appropriated.
> Assuming the graph is in 'camp' and the blocks are in 'campBlocks',
> this produces what you want:
> bl <- blocks(campBlocks)
> level <- as.vector(shortest.paths(hierarchy(campBlocks), 1)+1)
> data.frame(actor=V(camp)$name[unlist(bl)],
>           block=rep(seq_along(bl), sapply(bl, length)),
>           hierlevel=rep(level, sapply(bl, length)))
>> A related point. I started off by looking into Lambda Sets a la
>> Borgatti et al ( LS sets, lambda sets and other cohesive subsets. By
>> S. P. Borgatti, M. G. Everett, P. R. Shirey, Social Networks 12 (1990)
>> p. 337-357 ), but learned the superiority of cohesive blocking from
>> its Wiki page. However, I also found a remark in there that: "there is
>> a difference between the Peter McMahan's strict structural cohesion
>> algorithm and the Moody-White cohesive embedding algorithm". Has this
>> been fixed in igraph .6?
> I remember that in some wiki I've seen an example for which Peter's
> code was not working properly, and my implementation does. I think
> this example is included in the R manual page.
> But there is still some controversy with the definition of the method,
> the Moody-White paper is ambiguous. I would need to look more
> carefully to see what exactly the problem is.
>> Finally, I assume that cohesive blocking doesn't yet accommodate
>> weights, but please let me know if this is not the case.
> Weights are not supported, I am not even sure how they could be incorporated.
> Best,
> Gabor
>> Best regards,
>> Joe
>> _______________________________________________
>> igraph-help mailing list
>> address@hidden
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> --
> Gabor Csardi <address@hidden>     MTA KFKI RMKI
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