Thank you!
A bug cropped up: Warning message:
In .Call("R_igraph_subgraph", graph, as.igraph.vs(graph, v) - 1, :
At structural_properties.c:1945 :igraph_subgraph is deprecated from igraph 0.6, use igraph_induced_subgraph instead
well, I used induced.subgraph instead. But as I said, the nodes which will be interacting in between must not get lost. Here, only those 16 nodes are coming, if the interaction is via some node other than the one specified in 16, is not getting displayed. I want those nodes too in my subgraph.