Re: [igraph] Ask some questions about community.c

[Gabor Csardi]

Dear Zhongmin xiong,

On Wed, Sep 26, 2007 at 10:01:37AM +0800, address@hidden wrote:
> Dear Gabor Csardi,
> 
> I have some questions about the module community.c in the R source 
> package version of the latest release--igraph_0.4.3.tar.gz.
> 
> are the ids of the edges or the vectices,with which dealt  by the 
> function "igraph_community_eb_get_merges" and the  
> function "igraph_community_edge_betweenness",  number from zero? In 
> other words,if the number of vectices in a graph is n,the ids of the 
> vectices in this graph should be from zero to (n-1).

yes, that is correct, vertices and edges are numbered from zero.

> whether is it true that the vector "from" or "to" stores the vectices 
> of an edge,of which ids are number from zero, in the graph 
> structure "igraph_t"? 

from[0] -> to[0]
from[1] -> to[1]
...

You mean this way?
That is currently true, but personally i wouldn't rely on it as
it might change in the future. 

If you program in C, then use igraph_edge() function instead:
http://cneurocvs.rmki.kfki.hu/igraph/doc/html/ch06s02.html#igraph_edge
Or you can use IGRAPH_FROM and IGRAPH_TO, these are currently undocumented
though, they are defined in igraph.h.

> Also,are the eids of edges treated by the 
> module "community.c" number from zero?

I guess yes, but which function/variable you mean specifically?

Gabor

> I look forward to your help.
> 
> Best regards
> Zhongmin xiong
> 
> 
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-- 
Csardi Gabor <address@hidden>    MTA RMKI, ELTE TTK