i'm going to do as follow: as reading edgelist line by line, i add the vertices and edges by myself. during that process, i can add an attribute named "type", which is "b" for buyers, and "s" for sellers.
i have tested by small graph, it works.
That is a little surprising, because the 'type' attribute should be logical, i.e. TRUE or FALSE.
but it will be more slow i think, because i have to judge where a vertex or edge has existed, and the buyer id and seller id can't be considered as the vertex id, but as the name of the vertex.
To be honest, I don't really get it why it will be slow. Just create a network and assign a type attribute for all vertices at the same time, in the beginning.
Gabor
[...]