[igraph] subgraph gives duplicate edges

[Gang Su]

To graph fans,

I just tried igraph and it's such an awesome lib! After playing around 
for a while, i loaded some interaction network data with 2k vertices 
and 10k edges. However, when subgraphing this graph, i found it's 
giving me duplicate edges. I made sure that in the original dataset 
there's no duplicate edges at all.
So I wonder what's going on. Have anyone of you ran into similar problem?
Forexample: i subgraphed ~ 40 nodes with 377 edges, only 350 are 
unique. And checked the original graph is not directed.
Thanks!

Gang Su

PhD student
Bioinformatics training track
Program in Biomedical Sciences
University of Michigan, Ann Arbor
MI, 48105, U.S.A.