Re: [igraph] i can't find it, but there must be an easy was to reduce a graph

[Tamas Nepusz]

> What I call "reduced graph" in this context is a graph g' whose nodes are the 
> communities of g and an edge exist between two nodes of g' if there is at 
> least one edge between the two correspondent communities.
There is no such function in igraph yet, and the reason is that it is very hard 
to decide what to do with the vertex and edge attributes after collapsing the 
vertices of the same community into a single vertex. It is probably not 
meaningful to keep the vertex attributes, but keeping the edge attributes may 
make sense; i.e., when there is more than a single edge between communities, 
one may wish to add up the numeric attributes of the edges before collapsing 
them. We haven't really figured it out how a generic solution should behave, so 
you should try and do it by implementing a function for that in R. Maybe Gabor 
can conjure up an efficient solution using only a few lines of code in R.

-- 
Tamas