# diameter

From igraph v1.0.0
by Gabor Csardi

##### Diameter of a graph

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

- Keywords
- graphs

##### 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 an
- 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.`distnace`

Their distance.

##### See Also

##### 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)
```

*Documentation reproduced from package igraph, version 1.0.0, License: GPL (>= 2)*

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