Re: [igraph] capturing edge weights in g <- graph.data.frame?

[Jeff Hemsley]

Thank you.
Very helpful.

On Sat, Feb 16, 2013 at 2:25 PM, Tamás Nepusz <address@hidden> wrote:
>> I have a data.frame with two columns, FROM and TO. Each are names of
>> people where the person in FROM sent a message to the person in TO.
>> There are many cases where person X sends to Y, but graph.data.frame
>> doesn't appear to capture edge weight.
> Are the weights defined explicitly in your data frame as a third column? If 
> so, igraph should add it to the generated graph:
>
>> df <- data.frame(from=c("a", "b", "a"), to=c("b", "a", "c"), weight=c(1,3,1))
>> g <- graph.data.frame(df)
>> E(g)$weight
> [1] 1 3 1
>
> If the weights are not given in the data frame explicitly but you simply want 
> to use the number of email exchanges as weights, you can do this:
>
>> df <- data.frame(from=c("a", "b", "a"), to=c("b", "a", "b"))
>> g <- graph.data.frame(df)
>> E(g)$weight <- 1
>> g <- simplify(g, edge.attr.comb="sum")
>
> The call to graph.data.frame will simply create an unweighted graph where the 
> number of edges from X to Y will be equal to the number of messages sent by X 
> to Y. Then we simply assign a weight of 1 to each message and ask igraph to 
> collapse multiple edges into a single one while summing the edge attributes.
>
> --
> T.
>
>
> _______________________________________________
> igraph-help mailing list
> address@hidden
> https://lists.nongnu.org/mailman/listinfo/igraph-help



-- 
Jeff Hemsley
Doctoral Candidate
The Information School
University of Washington
http://staff.washington.edu/jhemsley/
http://somelab.net/author/jhemsley/
address@hidden