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## Re: [igraph] edge weights bipartite projection

 From: Moses Boudourides Subject: Re: [igraph] edge weights bipartite projection Date: Fri, 19 Oct 2012 17:32:28 +0300

```Thanks! I knew the idea but not the syntax. So I guess it could work
for any path length, right? --M

On Fri, Oct 19, 2012 at 5:26 PM, Gábor Csárdi <address@hidden> wrote:
> Moses,
>
> this is not very hard, you just calculate all shortest paths between
> A-vertices and keep the ones that are of length two. E.g.
>
> library(igraph)
> inc <- matrix(sample(0:1, 50, replace=TRUE), 10, 5)
> g <- graph.incidence(inc)
>
> all3Paths <- sapply(which(V(g)\$type), function(from) {
>   sp <- get.all.shortest.paths(graph=g, from=from, to=which(V(g)\$type))\$res
>   sp[ sapply(sp, length) == 3 ]
> })
> unlist(all3Paths, recursive=FALSE)
>
> Gabor
>
> On Fri, Oct 19, 2012 at 9:44 AM, Moses Boudourides
>> Gábor,
>>
>> Let me ask something which is irrelevant to this thread and I won't be
>> surprised if you tell me that it is already taken care in igraph (in
>> which case I'll be grateful if you could tell me exactly how - because
>> I'm extremely lazy when I come to searching into manuals). This is
>> what I would like to know:
>>
>> When projecting a bipartite graph, is it possible instead of taking
>> the number of 2-paths between two vertices to get explicitly the set
>> of all such 2-paths? Of course, this amounts to getting a list of
>> vertices of mode B establishing the 2-paths for any pair of vertices
>> of mode A.
>>
>> --Moses
>>
>> On Fri, Oct 19, 2012 at 4:30 PM, Gábor Csárdi <address@hidden> wrote:
>>> On Fri, Oct 19, 2012 at 8:36 AM, Florian Umlauf (CRIE)
>>> [...]
>>>> I am working with a bipartite weighted network.  So every edge has a
>>>> weight.
>>>> When I use the bipartite.projection() the old weights gets lost and the
>>>> bipartite.projection() return a weight where it sums up the number of
>>>> alternative connections.
>>>
>>> That is the default behavior, but you can customize it, see
>>> ?attribute.combination for details.
>>>
>>>> Is there a way to hold the old weights and sum them up for the projection?
>>>
>>> I am not sure what you mean by this. Isn't this what is happening now
>>> by default? Can you give a small example for what you want?
>>>
>>> Thanks,
>>> Gabor
>>>
>>>> Thank everyone for your help
>>>>
>>>> Florian
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> igraph-help mailing list
>>>> https://lists.nongnu.org/mailman/listinfo/igraph-help
>>>>
>>>
>>>
>>>
>>> --
>>> Gabor Csardi <address@hidden>     MTA KFKI RMKI
>>>
>>> _______________________________________________
>>> igraph-help mailing list
>>> https://lists.nongnu.org/mailman/listinfo/igraph-help
>>
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>
>
>
> --
> Gabor Csardi <address@hidden>     MTA KFKI RMKI
>
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