Number of Vertex (vcount) is one more than the actual
I am learning about igraph and get stuck on vcount.
The edgelist in triangle.txt:
1 2
2 3
3 1
> g<- read_graph("triangle.txt", format="edgelist")
> g
IGRAPH 35ad1ec D--- 4 3 --
+ edges from 35ad1ec:
[1] 2->3 3->4 4->2
> vcount(g)
[1] 4
It is clear that the number of vertex is 3 from the edgelist, but why R give the number of vertex is 4.
I did experiment with with two other edgelists, with number of vertex 4 and 34, they gives 5 and 35.
Thank you.