The request of the vertex the degree of which is 0.

[Eunjae Lee]

I looked that the vertex, the degree of which is 0, is requested at Flash-Graph.
This vertex does not have a adj list.
This request loads just the header of the vertex like vertex ID, degree and offset.
But, they also exist in vertex-index that is in memory.
I wonder why the vertex, the degree of which is 0, is requested.

[Da Zheng]

This problem comes up from others as well. Right now, FlashGraph assumes that vertex Ids are integers and all Ids that fall between 0 and max Id correspond to vertices. If a vertex Id doesn't appear in the edge list, FlashGraph assumes it's an empty vertex (whose degree is 0). If you want to remove these empty vertices, you can do it with its R interface:

> deg <- fg.degree(g)
> subg <- fg.fetch.subgraph(g, which(deg > 0), compress=TRUE)