Re: [igraph] add.edges error message

[Alisa Coffin]

Thank you for your help Gabor. This was, if fact the problem, but it stemmed from an earlier issue of extracting the information from a GIS network dataset. I used the OID instead of the EID, which I should have used. Then subtracting one made it work out.

Alisa.

On Sat, Feb 23, 2008 at 2:37 PM, Gabor Csardi <address@hidden> wrote:

Alisa, without looking at your data, i can only guess that
this is the infamous "0-based ids" trick. igraph vertices are
numbered from zero. If indeed this is the problem, then you can solve
it by subtracting one from the edges:

g2005 <- add.edges(g2005, t(edges2005)-1)

Btw. the error message means that in your edge matrix the ids are
not between 0 and number_of_vertices-1.

Gabor

On Sat, Feb 23, 2008 at 02:23:11PM -0500, Alisa Coffin wrote:
> Hello,
>
> I am brand new to using igraph, and relatively new to R, so please bear with me
> if my question is a simple one. I am building a graph using the example given
> in the "Real world examples" of the igraph introductory material. I have been
> successful so far in creating the graph, adding vertices, and creating a matrix
> of edges. However, when it comes to adding the edges to the graph, I get an
> error message:
>
> > g2005 <- add.edges(g2005, t(edges2005))
> Error in add.edges(g2005, t(edges2005)) :
>   At type_indexededgelist.c:240 : cannot add edges, Invalid vertex id
>
> I'm not sure what this means. I have tried looking at the vertex list and the
> edge list and can't seem to find a problem with either. Any ideas? Any
> workarounds?
>
> Thank you very much!
> Alisa
>
>
>
> --
> Alisa Coffin, PhD. Candidate
> Department of Geography
> University of Florida
> Gainesville, FL  32611

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--
Csardi Gabor <address@hidden>    UNIL DGM


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-- 
Alisa Coffin, PhD. Candidate
Department of Geography
University of Florida
Gainesville, FL  32611