[R] igraph: Turn multiple edges into weights

[Rui Barradas]

Hello,

There is a function count.multiple that can be used to do what you 
want.  You can also have a function return unique rows/edges. Here are 
three functions that count multiple edges.

library(igraph)
ee <- c(1,2,2,3,1,2,2,4,1,2,2,3)
g <- graph(ee)

plot(g)

# Returns a two column matrix with edge names and counts
edge.count1 <- function(g){
     result <- cbind(E(g), count.multiple(g))
     colnames(result) <- c("edge", "count")
     result
}

# Returns a three column matrix with edges and counts
edge.count2 <- function(g){
     cbind(get.edgelist(g), count.multiple(g))
}

# Adapted from R-Help:
#    G. Jay Kerns
#    Dec 22, 2007; 11:55pm
#    Re: number of count of each unique row
# Returns a data.frame of unique edges and counts
edge.count3 <- function(g){
     D <- data.frame(get.edgelist(g))  # convert to data frame
     ones <- rep(1, nrow(D))   # a column of 1s
     result <- aggregate(ones, by = as.list(D), FUN = sum)
     names(result) <- c("from", "to", "count")
     result
}

edge.count1(g)
edge.count2(g)
edge.count3(g)

Hope this helps,

Rui Barradas

Em 14-08-2012 22:09, Jonas Michaelis escreveu:
> Dear all,
>
>
> I have some network data - about 300 vertices and several thousand edges. I
> am looking for a way to turn multiple edges into weights of the edges. I
> looked around and - surprisingly? - haven't found anything. Is there an
> easy way to do this?
>
>
> Best, Jonas
>
> 	[[alternative HTML version deleted]]
>
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