Re: [R] vertex labels in igraph from adjacency matrix

From: Gabor Csardi <csardi_at_rmki.kfki.hu>
Date: Wed, 05 Mar 2008 10:32:46 +0100

Mark, graph.adjacency always preserves the order of the vertices, so the vertex at row/column 1 will be vertex #0 in the igraph graph, etc. I'll document this in a minute.

This means that you can always do

g <- graph.adjacency(A)
V(g)$name <- colnames(A)

But i completely agree that this should be done by default, i'll do that in the near future.

Btw, weighted shortest path calculation (= where the edges have weights or capacities) is only implemented in the development version of igraph. Just in case you're looking for that.

Best,
Gabor

On Wed, Mar 05, 2008 at 01:39:41AM -0500, Mark W Kimpel wrote:
> I am getting some unexpected results from some functions of igraph and
> it is possible that I am misinterpreting the vertex numbers. Eg., the
> max betweenness measure seems to be from a vertex that is not connected
> to a single other vertex. Below if my code snippet:
>
> require(igraph)
> my.graph <- graph.adjacency(adjmatrix = my.adj.matrix, mode=c("undirected"))
>
> most.between.vert <- colnames(my.adj.matrix)[which(betweenness(graph =
> my.graph, v=V(my.graph), directed = FALSE) == max(betweenness(graph =
> my.graph, v=V(my.graph), directed = FALSE))) + 1]
>
> sum(my.adj.matrix[most.between.vertext,])
> 0
>
>
> Is there a way to automatically set the vertex name attributes from the
> row and colnames of the inputted adjacency matrix to graph.adjacency?
> This would seem like an intuitive feature, but I can't find it
> documented. In the absence of this feature, how can I make sure that I
> am setting the vertex name attributes correctly?
> --
>
> Mark W. Kimpel MD ** Neuroinformatics ** Dept. of Psychiatry
> Indiana University School of Medicine
>
> 15032 Hunter Court, Westfield, IN 46074
>
> (317) 490-5129 Work, & Mobile & VoiceMail
> (317) 204-4202 Home (no voice mail please)
>
> mwkimpel<at>gmail<dot>com
>
> ******************************************************************

-- 
Csardi Gabor <csardi_at_rmki.kfki.hu>    UNIL DGM

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