# R igraph manual pages

Use this if you are using igraph from R

## Neighborhood of graph vertices

### Description

These functions find the vertices not farther than a given limit from another fixed vertex, these are called the neighborhood of the vertex.

### Usage

```ego_size(graph, order = 1, nodes = V(graph), mode = c("all", "out",
"in"), mindist = 0)

ego(graph, order = 1, nodes = V(graph), mode = c("all", "out", "in"),
mindist = 0)

make_ego_graph(graph, order = 1, nodes = V(graph), mode = c("all",
"out", "in"), mindist = 0)
```

### Arguments

 `graph` The input graph. `order` Integer giving the order of the neighborhood. `nodes` The vertices for which the calculation is performed. `mode` Character constant, it specifies how to use the direction of the edges if a directed graph is analyzed. For ‘out’ only the outgoing edges are followed, so all vertices reachable from the source vertex in at most `order` steps are counted. For ‘"in"’ all vertices from which the source vertex is reachable in at most `order` steps are counted. ‘"all"’ ignores the direction of the edges. This argument is ignored for undirected graphs. `mindist` The minimum distance to include the vertex in the result.

### Details

The neighborhood of a given order `o` of a vertex `v` includes all vertices which are closer to `v` than the order. Ie. order 0 is always `v` itself, order 1 is `v` plus its immediate neighbors, order 2 is order 1 plus the immediate neighbors of the vertices in order 1, etc.

`ego_size` calculates the size of the neighborhoods for the given vertices with the given order.

`ego` calculates the neighborhoods of the given vertices with the given order parameter.

`make_ego_graph` is creates (sub)graphs from all neighborhoods of the given vertices with the given order parameter. This function preserves the vertex, edge and graph attributes.

`connect` creates a new graph by connecting each vertex to all other vertices in its neighborhood.

### Value

`ego_size` returns with an integer vector.

`ego` returns with a list of integer vectors.

`make_ego_graph` returns with a list of graphs.

`connect` returns with a new graph object.

### Author(s)

Gabor Csardi csardi.gabor@gmail.com, the first version was done by Vincent Matossian

### Examples

```
g <- make_ring(10)
ego_size(g, order = 0, 1:3)
ego_size(g, order = 1, 1:3)
ego_size(g, order = 2, 1:3)
ego(g, order = 0, 1:3)
ego(g, order = 1, 1:3)
ego(g, order = 2, 1:3)

# attributes are preserved
V(g)\$name <- c("a", "b", "c", "d", "e", "f", "g", "h", "i", "j")
make_ego_graph(g, order = 2, 1:3)

# connecting to the neighborhood
g <- make_ring(10)
g <- connect(g, 2)

```

[Package igraph version 1.2.4.1 Index]