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

From: Gabor Csardi <>
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.


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 <>    UNIL DGM

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Received on Wed 05 Mar 2008 - 09:34:58 GMT

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