Re: [igraph] Creating new graph from existing graph with only top 10 percent of edges

[Tamás Nepusz]

Hi Alex, 

subgraph.edges was added in 0.6 so you can try upgrading your igraph 
installation to the latest version. An alternative to subgraph.edges is to 
_delete_ the edges you don't need using delete.edges.

> I use weights <- E(g1)$weight to get all the edge weights. My idea then was 
> to use quantile(weights, 0.9) to return the 90% edge weight, and then create 
> the graph g2 using g2 <- delete.edges(g1,which(E(g1)$weight<=0.2455)) if 
> 0.2455 was the 90th percent edge weight returned by the quantile function.
You were bitten by the 0-based indexing of igraph 0.5.x and below (igraph 0.6 
uses 1-based indexing). Basically, the indices that R returns from which() are 
1-based, so you need to subtract 1 from them to convert them to igraph edge 
IDs. You need this only if you use igraph 0.5.x or below.

Best,
T.