igraph (version 1.3.5)

# edge_density: Graph density

## Description

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

## Usage

`edge_density(graph, loops = FALSE)`

## Value

A real constant. This function returns `NaN` (=0.0/0.0) for an empty graph with zero vertices.

## 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.

## Author

Gabor Csardi csardi.gabor@gmail.com

## Details

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

## References

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

`vcount`, `ecount`, `simplify` to get rid of the multiple and/or loop edges.

## Examples

Run this code
``````
g1 <- make_empty_graph(n=10)
g2 <- make_full_graph(n=10)
g3 <- sample_gnp(n=10, 0.4)

# loop edges
g <- graph( c(1,2, 2,2, 2,3) )
edge_density(g, loops=FALSE)              # this is wrong!!!
edge_density(g, loops=TRUE)               # this is right!!!
edge_density(simplify(g), loops=FALSE)    # this is also right, but different

``````

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