igraph (version 0.3.2)

graph.density: Graph density

Description

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

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.

Value

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

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.

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