# graph.density

From igraph v0.5.5-3
by Gabor Csardi

##### Graph density

The density of a graph is the ratio of the number of edges and the number of possible edges.

- Keywords
- graphs

##### Usage

`graph.density(graph, loops=FALSE)`

##### Arguments

- graph
- The input graph.
- loops
- Logical constant, whether to allow loop edges in the graph. If this is TRUE then self loops are considered to be possible. If this is FALSE then we assume that the graph does not contain any loop edges and that loop edges are not meaningful.

##### Details

Note that this function may return strange results for graph with multiple edges, density is ill-defined for graphs with multiple edges.

##### Value

- A real constant. This function returns
`NaN`

(=0.0/0.0) for an empty graph with zero vertices.

##### concept

Graph density

##### References

Wasserman, S., and Faust, K. (1994). Social Network Analysis: Methods and Applications. Cambridge: Cambridge University Press.

##### See Also

`vcount`

, `ecount`

,
`simplify`

to get rid of the multiple and/or loop edges.

##### Examples

```
g1 <- graph.empty(n=10)
g2 <- graph.full(n=10)
g3 <- erdos.renyi.game(n=10, 0.4)
# loop edges
g <- graph( c(0,1, 1,1, 1,2) )
graph.density(g, loops=FALSE) # this is wrong!!!
graph.density(g, loops=TRUE) # this is right!!!
graph.density(simplify(g), loops=FALSE) # this is also right, but different
```

*Documentation reproduced from package igraph, version 0.5.5-3, License: GPL (>= 2)*

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