If attributes are supplied, and they are not present in the graph,
their values for the original vertices of the graph are set to
`NA`

.

## Usage

`add_vertices(graph, nv, ..., attr = list())`

## Arguments

- graph
The input graph.

- nv
The number of vertices to add.

- ...
Additional arguments, they must be named, and they will be added as vertex attributes, for the newly added vertices. See also details below.

- attr
A named list, its elements will be added as vertex attributes, for the newly added vertices. See also details below.

## See also

Other functions for manipulating graph structure:
`+.igraph()`

,
`add_edges()`

,
`complementer()`

,
`compose()`

,
`connect()`

,
`contract()`

,
`delete_edges()`

,
`delete_vertices()`

,
`difference.igraph()`

,
`difference()`

,
`disjoint_union()`

,
`edge()`

,
`igraph-minus`

,
`intersection.igraph()`

,
`intersection()`

,
`path()`

,
`permute()`

,
`rep.igraph()`

,
`reverse_edges()`

,
`simplify()`

,
`union.igraph()`

,
`union()`

,
`vertex()`

## Examples

```
g <- make_empty_graph() %>%
add_vertices(3, color = "red") %>%
add_vertices(2, color = "green") %>%
add_edges(c(
1, 2,
2, 3,
3, 4,
4, 5
))
g
#> IGRAPH 530bb9f D--- 5 4 --
#> + attr: color (v/c)
#> + edges from 530bb9f:
#> [1] 1->2 2->3 3->4 4->5
V(g)[[]]
#> + 5/5 vertices, from 530bb9f:
#> color
#> 1 red
#> 2 red
#> 3 red
#> 4 green
#> 5 green
plot(g)
```