# R igraph manual pages

Use this if you are using igraph from R

 diameter {igraph} R Documentation

## Diameter of a graph

### Description

The diameter of a graph is the length of the longest geodesic.

### Usage

diameter(graph, directed = TRUE, unconnected = TRUE, weights = NULL)

### Arguments

 graph The graph to analyze. directed Logical, whether directed or undirected paths are to be considered. This is ignored for undirected graphs. unconnected Logical, what to do if the graph is unconnected. If FALSE, the function will return a number that is one larger the largest possible diameter, which is always the number of vertices. If TRUE, the diameters of the connected components will be calculated and the largest one will be returned. weights Optional positive weight vector for calculating weighted distances. If the graph has a weight edge attribute, then this is used by default.

### Details

The diameter is calculated by using a breadth-first search like method.

get_diameter returns a path with the actual diameter. If there are many shortest paths of the length of the diameter, then it returns the first one found.

farthest_vertices returns two vertex ids, the vertices which are connected by the diameter path.

### Value

A numeric constant for diameter, a numeric vector for get_diameter. farthest_vertices returns a list with two entries:

• vertices The two vertices that are the farthest.

• distance Their distance.

### Author(s)

Gabor Csardi csardi.gabor@gmail.com

### Examples

g <- make_ring(10)
g2 <- delete_edges(g, c(1,2,1,10))
diameter(g2, unconnected=TRUE)
diameter(g2, unconnected=FALSE)

## Weighted diameter
set.seed(1)
g <- make_ring(10)
E(g)\$weight <- sample(seq_len(ecount(g)))
diameter(g)
get_diameter(g)
diameter(g, weights=NA)
get_diameter(g, weights=NA)

[Package igraph version 1.3.1 Index]