Re: [igraph] combining communities

[Gábor Csárdi]

On Mon, Aug 9, 2010 at 2:19 PM, Claudia Muller-Birn <address@hidden> wrote:
> Hi Gabor,
>
> On Aug 9, 2010, at 4:16 AM, Gábor Csárdi wrote:
>
>> Sorry this was not complete yet, I mean
>>
>> g <-  simplify(as.undirected(ba.game(100, 3)))
>> sc <- spinglass.community(g)$membership
>> el <- get.edgelist(g)
>> for (i in seq_len(max(sc)+1)-1) {
>>  w <- which(sc==i)-1
>>  el[ el %in% w ] <- w[1]
>> }
>> mode(el) <- "character"
>> el <- unique(el)
>> graph.edgelist(el, dir=FALSE)
>>
>> You can remove the loop edges before creating the graph:
>> el <- el[ el[,1] != el[,2], ]
>
> Interesting solution. But unfortunately, I am not experienced enough to 
> understand every step. Do you mind to extend your code by some comment lines 
> (starting with the for loop)? That would be great. Thank you very much!

The loops iterates over the communities. From each community we the
take the id of the first vertex and replace the ids of all other
vertices with this one in the edge list.

The rest is not very important, the "mode(el)" line is needed because
the vertex ids are not consecutive any more in the edge list matrix
and thus we want to use them as symbolic vertex names. The "unique"
line removes the duplicate edges.

Best,
Gabor

>> Best,
>> Gabor
>
> Claudia
>
>>
>> On Mon, Aug 9, 2010 at 10:07 AM, Gábor Csárdi <address@hidden> wrote:
>>> Hi,
>>>
>>> in igraph 0.6 we have a function for that (contract.vertices in R),
>>> but it should not be too hard to code a quick solution in R. E.g.
>>>
>>> g <- erdos.renyi.game(100, 1/100)
>>> sc <- spinglass.community(g)$membership
>>> el <- get.edgelist(g)
>>> for (i in seq_len(max(sc)+1)-1) {
>>>
>>> }
>>>
>>> On Mon, Aug 9, 2010 at 2:33 AM, Stuart Kininmonth
>>> <address@hidden> wrote:
>>>> Hi,
>>>>
>>>> just wondering if anyone has written any code to take a community 
>>>> membership identity list and combine the nodes and arcs to create a 
>>>> community network?
>>>>
>>>> thanks,
>>>>
>>>> Stuart Kininmonth
>>>> Spatial Ecologist
>>>> Australian Institute of Marine Science
>>>>
>>>>
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>>>
>>>
>>>
>>> --
>>> Gabor Csardi <address@hidden>     UNIL DGM
>>>
>>
>>
>>
>> --
>> Gabor Csardi <address@hidden>     UNIL DGM
>>
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-- 
Gabor Csardi <address@hidden>     UNIL DGM