Re: [igraph] reordering the vertex sequence

[Magnus Thor Torfason]

On 5/30/2011 23:03, Gábor Csárdi wrote:
> Dear Prof Freeman,
>
> On Sat, May 28, 2011 at 10:12 AM, Lin Freeman<address@hidden>  wrote:
> > How can I get the vertices into the order I want?
>
> there are two possibilities. You can permute the vertices after
> reading in the graph, with permute.vertices(). But it is much simpler
> to use the (undocumented, sorry), 'predef' argument to read.graph(),
> which can explicitly give the vertex names, in the right order:
>
> G<- read.graph("zach.txt", format="ncol", weights=TRUE, names=TRUE,
> predef=as.character(1:34))
>
> Btw. please remember, that the numeric igraph vertex ids start with
> zero in igraph 0.5.x, so they are not the same as the ids in your
> graph.
>
> Best,
> Gabor

There's also a third possibility, which only requires a tiny bit more 
work, but does not depend on any undocumented interfaces (which is a
plus for me):

> library(igraph)
> d.edges        <- read.delim("Data/Network.dat", header=FALSE)
> names(d.edges) <- c("V1","V2","weight")
> d.vertices     <- data.frame(vertices=1:34)
> g              <- graph.data.frame(d.edges, vertices=d.vertices)
> V(g)$name
 [1] "1"  "2"  "3"  "4"  "5"  "6"  "7"  "8"  "9"  "10"
[11] "11" "12" "13" "14" "15" "16" "17" "18" "19" "20"
[21] "21" "22" "23" "24" "25" "26" "27" "28" "29" "30"
[31] "31" "32" "33" "34"
> E(g)$weight
 [1] 4 5 6 3 3 3 3 3 3 2 5 2 4 4 3 2 5 1 2 3 3 3 1 3 3 5
[27] 3 3 3 3 2 1 2 2 2 2 5 2 2 4 3 2 3 4 2 3 2 2 7 2 2 3
[53] 3 3 1 3 2 5 4 3 4 4 2 3 2 4 2 1 1 3 4 2 4 2 2 3 4 5

In other words, passing a separate data.frame with a list of vertices to 
graph.data.frame seems to ensure the desired ordering. I guess the fact 
that passing the vertices argument to graph.data.frame ensures correct 
ordering may not be documented but the functionality is the one I would 
intuitively have expected.

Best,
Magnus