# V: Vertices of a graph In igraph: Network Analysis and Visualization

## Description

Create a vertex sequence (vs) containing all vertices of a graph.

## Usage

 `1` ```V(graph) ```

## Arguments

 `graph` The graph

## Details

A vertex sequence is just what the name says it is: a sequence of vertices. Vertex sequences are usually used as igraph function arguments that refer to vertices of a graph.

A vertex sequence is tied to the graph it refers to: it really denoted the specific vertices of that graph, and cannot be used together with another graph.

At the implementation level, a vertex sequence is simply a vector containing numeric vertex ids, but it has a special class attribute which makes it possible to perform graph specific operations on it, like selecting a subset of the vertices based on graph structure, or vertex attributes.

A vertex sequence is most often created by the `V()` function. The result of this includes all vertices in increasing vertex id order. A vertex sequence can be indexed by a numeric vector, just like a regular R vector. See `[.igraph.vs` and additional links to other vertex sequence operations below.

## Value

A vertex sequence containing all vertices, in the order of their numeric vertex ids.

## Indexing vertex sequences

Vertex sequences mostly behave like regular vectors, but there are some additional indexing operations that are specific for them; e.g. selecting vertices based on graph structure, or based on vertex attributes. See `[.igraph.vs` for details.

## Querying or setting attributes

Vertex sequences can be used to query or set attributes for the vertices in the sequence. See `\$.igraph.vs` for details.

Other vertex and edge sequences: `E()`, `igraph-es-attributes`, `igraph-es-indexing2`, `igraph-es-indexing`, `igraph-vs-attributes`, `igraph-vs-indexing2`, `igraph-vs-indexing`, `print.igraph.es()`, `print.igraph.vs()`

## Examples

 ```1 2 3 4 5 6 7 8``` ```# Vertex ids of an unnamed graph g <- make_ring(10) V(g) # Vertex ids of a named graph g2 <- make_ring(10) %>% set_vertex_attr("name", value = letters[1:10]) V(g2) ```

### Example output

```Attaching package: 'igraph'

The following objects are masked from 'package:stats':

decompose, spectrum

The following object is masked from 'package:base':

union

+ 10/10 vertices, from 60e1ac0:
[1]  1  2  3  4  5  6  7  8  9 10
+ 10/10 vertices, named, from 40650c0:
[1] a b c d e f g h i j
```

igraph documentation built on Jan. 8, 2021, 2:19 a.m.