Re: [igraph] subgraph in igraph

[Gábor Csárdi]

How is this different from just calling induced.subgraph()? (Apart from being slower for small subgraphs of large graphs.)

> g <- graph.ring(10)

> V(g)$name <- LETTERS[1:10]

> get.edgelist(get_sub_graph(6:10, g), names = FALSE)

     [,1] [,2]

[1,]    1    2

[2,]    2    3

[3,]    3    4

[4,]    4    5

> get.edgelist(induced.subgraph(g, 6:10), names = FALSE)

     [,1] [,2]

[1,]    1    2

[2,]    2    3

[3,]    3    4

[4,]    4    5

G.

On Sun, May 3, 2015 at 5:47 PM, Peidong Chen <address@hidden> wrote:

I think it is better to define functions by our own.

get_sub_graph <- function(subGraphNodes,g)

{

  nonSubGraphNodes <- which(!((1:vcount(g)) %in% subGraphNodes))

  subGraph <- delete.vertices(g , nonSubGraphNodes)

  subGraph

}

2015-05-03 14:24 GMT-07:00 Fatemeh a <address@hidden>:

thanks for your reply.

 this question raised because as you mention  "induced.subgraph"actually dose that , but I checked it  when we keep delete.vertices = FALSE and with one small example it dosen't change that, but i can't be sure and generalized it, so what about when we keep the vertices  ?

On Mon, May 4, 2015 at 1:39 AM, Peidong Chen <address@hidden> wrote:

I think it changes nodes indices, because like "induced.subgraph" function creates a totally new indices different from the original graph

2015-05-03 14:07 GMT-07:00 Fatemeh a <address@hidden>:

Hi all,

I have a question regards subgraph, dose supgraph.edges function changes nodes indices?  

thank you in advance,

Fatemeh

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regards

F..A

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