[igraph] Vertex from an edge

[Alvaro Graves Fuenzalida]

Hi,

I'm using the R version of igraph and a was wondering how to do the 
following: For each edge, I need to take the values of each node (stored 
in an node's attribute) and sum them but is not clear to me how to use 
the nodes from an edge. I assume is something related to E(g) but I 
couldn't find what other parameter.

Thanks in advance.