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## Re: [igraph] segmenting graphs

**From**: |
Tom Wright |

**Subject**: |
Re: [igraph] segmenting graphs |

**Date**: |
Mon, 05 May 2014 16:42:43 -0400 |

Whoops sorry,
t<-graph.empty()
t<-t+vertices(c('r',LETTERS[1:9]))
t['r',LETTERS[1:9],attr='weight']<-c(1,-2,2,-2,2,-6,5,10,-10)
t['A','B']<-1
t['r','A']<-FALSE
I'm trying to implement the Lerchs Grossman algorithm, one step includes
finding the subgraph V{B,A}, detaching it from 'r' and adding it as a
child of 'C'. The new edge C -> B needs to be assigned the summed weight
of the detached subgraph V{B,A}.
Apologies if my terminology is poor, I'm still trying to get this clear
in my head as well as in code.
On Mon, 2014-05-05 at 16:26 -0400, Gábor Csárdi wrote:
>* On Mon, May 5, 2014 at 4:18 PM, Tom Wright <address@hidden> wrote:*
>* Hi,*
>* I'm trying to use iGraph in the R environment and I'm getting*
>* confused.*
>* It seems to me that what I want to do should be simple but...*
>* *
>* t<-graph.empty()*
>* t<-t+vertices(c('r',LETTERS[1:9]))*
>* t['r',D.vertices[,1],attr='weight']<-1*
>* *
>* *
>* Error in as.igraph.vs(x, j) : object 'D.vertices' not found*
>* *
>* t['A','B']<-1*
>* t['r','A']<-FALSE*
>* *
>* I want to get the subgraph with vertex 'A' as the root, i.e.*
>* vertices*
>* {'A','B'}*
>* *
>* *
>* What does this really mean? The whole tree rooted at 'A'? *
>* *
>* *
>* graph.neighborhood(t, 'A', order=vcount(t))[[1]]*
>* *
>* *
>* Or something else?*
>* *
>* *
>* Gabor*
>* *
>* *
>* [...]*
>* _______________________________________________*
>* igraph-help mailing list*
>* address@hidden*
>* https://lists.nongnu.org/mailman/listinfo/igraph-help*