Use this if you are using igraph from R
| c.igraph.vs {igraph} | R Documentation | 
Concatenate vertex sequences
## S3 method for class 'igraph.vs'
c(..., recursive = FALSE)
... | 
 The vertex sequences to concatenate. They must refer to the same graph.  | 
recursive | 
 Ignored, included for S3 compatibility with
the base   | 
A vertex sequence, the input sequences concatenated.
Other vertex and edge sequence operations: 
c.igraph.es(),
difference.igraph.es(),
difference.igraph.vs(),
igraph-es-indexing2,
igraph-es-indexing,
igraph-vs-indexing2,
igraph-vs-indexing,
intersection.igraph.es(),
intersection.igraph.vs(),
rev.igraph.es(),
rev.igraph.vs(),
union.igraph.es(),
union.igraph.vs(),
unique.igraph.es(),
unique.igraph.vs()
g <- make_(ring(10), with_vertex_(name = LETTERS[1:10]))
c(V(g)[1], V(g)['A'], V(g)[1:4])