[BioC] R graphs: all paths lengths between two nodes in a directed graph

[Li Long]

you can take a look at BioC/RBGL package, which contains quite a number of
often-used graph algorithms.

Li

> I would need help in obtaining all path lengths between two nodes in a
> directed graph.
>
> Suppose I have the following directed graph (below) called "mygraph":
>
>> library(graph)
>>
>> y <- as.character(seq(1,6))
>> rel <- list(c(2,4), c(3,5), 6, 5, 6, NULL)
>> edgelength <- list(c(0,1), c(0,2), 3, 0, 0, "NA")
>>
>> edL=vector("list", length=(length(y)))
>> names(edL)=y
>> for(l in 1:(length(y)))
> + {edL[[l]]=list(edges=rel[[l]], weights=edgelength[[l]])}
>>
>> mygraph=new("graphNEL", nodes = y, edgeL = edL, edgemode = "directed")
>> mygraph
> A graphNEL graph with directed edges
> Number of Nodes = 6
> Number of Edges = 7
>> edges(mygraph)
> $`1`
> [1] "2" "4"
>
> $`2`
> [1] "3" "5"
>
> $`3`
> [1] "6"
>
> $`4`
> [1] "5"
>
> $`5`
> [1] "6"
>
> $`6`
> character(0)
>
>> edgeWeights(mygraph)
> $`1`
> 2 4
> 0 1
>
> $`2`
> 3 5
> 0 2
>
> $`3`
> 6
> 3
>
> $`4`
> 5
> 0
>
> $`5`
> 6
> 0
>
> $`6`
> numeric(0)
>
> I am striving to get the lengths of all possible paths between nodes "1"
> and "6", which are:
>
> 1 --> 2 --> 3 --> 6 : length 0+0+3=3
> 1 --> 2 --> 5 --> 6 : length 0+2+0=2
> 1 --> 4 --> 5 --> 6 : length 1+0+0=1
>
> What would be a clever way to accomplish this in R?  Thank you.
>
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