[igraph] Re: Assign Weight to Link by Counting Repetitions

[Lorenzo Isella]

> Date: Fri, 2 Oct 2009 12:17:32 +0200
> From: G?bor Cs?rdi <address@hidden>
> Subject: Re: [igraph] Assign Weight to Link by Counting Repetitions
> To: Help for igraph users <address@hidden>
> Message-ID:
>         <address@hidden>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Lorenzo,
>
> see ?count.multiple, the last example on the manual page actually does
> exactly what you want.
>
> Best,
> Gabor
>   

Dear Gabor and dear Tamas,
Thanks for your suggestions, which both answer my question.
Now, there is only one thing that bothers me: how to remove vertexes 
when I use numbers as vertex names.
See the code snippet to read the adjacency list (saved in file 
graph_test.dat and copied at the end of the email)

rm(list=ls())
library(igraph)

tab <- read.table("graph_test.dat",header=FALSE)

g <- graph.data.frame(tab, dir=FALSE)

E(g)$weight <- count.multiple(g)

g <- simplify(g)


I then get easily the properties of the graph

> g
Vertices: 4
Edges: 2
Directed: FALSE
Edges:
                            
[0] '174514432' -- '95879170'
[1] '74514432'  -- '95879170'
> V(g)
Vertex sequence:
[1] "174514432" "78774272"  "74514432"  "95879170"

and I can e.g. remove vertex 1 by issuing the command

> delete.vertices(g, V(g)[1])

However, in general I read  the ID's of the vertices to be removed from 
another file. Neither using them as an array or as strings works for me.
E.g. if I re-read the graph and try to get rid of its first vertex by 
using its ID as printed out above

> delete.vertices(g, "174514432")
Error in delete.vertices(g, "174514432")
At iterators.c:721 : Cannot create iterator, invalid vertex id, Invalid 
vertex id

or as a numeric array

> delete.vertices(g, c(74514432))
Error in delete.vertices(g, c(74514432)) :
 At iterators.c:721 : Cannot create iterator, invalid vertex id, 
Invalid vertex id


In other words: which kind of data type is V(g)[1]? It looks like a 
string, but probably it is not (and should not be, according to the 
delete.vertices documentation).
Many thanks

Lorenzo


174514432 95879170
78774272 78774272
74514432 95879170
78774272 78774272
74514432 95879170
78774272 78774272
74514432 95879170
78774272 78774272
74514432 95879170
78774272 78774272
74514432 95879170
78774272 78774272
74514432 95879170
78774272 78774272
74514432 95879170
78774272 78774272
74514432 95879170
78774272 78774272
74514432 95879170
78774272 78774272
74514432 95879170