Re: [igraph] Character Vectors Containing Vertex Names

[Gábor Csárdi]

Dear Lorenzo,

On Thu, Oct 7, 2010 at 4:36 PM, Lorenzo Isella <address@hidden> wrote:
> Dear All,
> I have just updated my igraph installation.
> When I looked at the news in the R interface, I read the following
>
>> All functions that have vertex id input parameters, handle character
>> vectors containing vertex names now.
>
> I remember (though I cannot find the precise email) that this was
> anticipated some months ago in a reply to an email of mine on this very
> mailing list.
> In particular, I wonder if this could be useful to simplify a bit the
> procedure I follow when translating an edge list stored into a text file,
> where every node is given by a symbolic ID (just a number in this case, but
> it could be something else) into an igraph graph.

this change does not affect the symbolic edge list -> igraph
conversion as far as I see it. It rather simplifies the opposite:
instead of vertex ids, you can just use your symbolic vertex names to
select/delete/etc. vertices.

Btw. I think that the symbolic edge list -> igraph conversion is not
very difficult, in your code it takes two lines, if you use
read.graph(format="ncol", ...) it takes only one function call. It
cannot really be simpler than that.

Best,
Gabor

> To fix the ideas, see the code snippet below followed by the corresponding
> input file.
> Any thoughts are appreciated.
> Cheers
>
> Lorenzo
>
>
> ########################################################
>
> library(igraph)
> library(Cairo)
>
>
> tab <- read.table("my_net.dat", header=FALSE)
>
>
>
> g <- graph.data.frame(tab, dir=FALSE) #create graph where the numbers
> providing the visitor ID are
>
> g <- simplify(g)
>
> d <- get.diameter(g,weights=NA)
>
>
>
>
> l <- layout.fruchterman.reingold(g)
>
> l <- layout.norm(l, -1,1, -1,1)
>
>
> CairoPDF("large_network.pdf")
>
> plot(g, layout=l,
>     vertex.label.dist=0.5,   vertex.color="#ff000033",
>     vertex.frame.color="#ff000033", edge.color="#55555533",vertex.label=NA,
> vertex.size=4
>     #, main=week[sel_day]
> #as.expression(c(sprintf("Power = %.3f", power))) ,cex=1.2)
>     #,ylab=as.expression(c(sprintf("Week %1d",k)))
>     )
>
>
>
> V(g)$id <- seq(vcount(g))-1
> g2 <- subgraph(g, d)
>
>
> plot(g2, layout=l[ V(g2)$id+1, ],
> vertex.color="blue", vertex.frame.color="blue",
>   edge.color="blue",vertex.label=NA, edge.width=2, vertex.size=4,
>   add=TRUE, rescale=FALSE)
>
>
>
> dev.off()
>
>
> ##################################
>
>
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>
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>



-- 
Gabor Csardi <address@hidden>     UNIL DGM