rgraph {sna} | R Documentation

## Generate Bernoulli Random Graphs

### Description

`rgraph` generates random draws from a Bernoulli graph distribution, with various parameters for controlling the nature of the data so generated.

### Usage

    rgraph(n, m=1, tprob=0.5, mode="digraph", diag=FALSE, replace=FALSE,
        tielist=NULL)

### Arguments

`n` | The size of the vertex set (|V(G)|) for the random graphs
`m` | The number of graphs to generate
`tprob` | Information regarding tie (edge) probabilities; see below
`mode` | ``digraph'' for directed data, ``graph'' for undirected data
`diag` | Should the diagonal entries (loops) be set to zero?
`replace` | Sample with or without replacement from a tie list (ignored if `tielist==NULL`
`tielist` | A vector of edge values, from which the new graphs should be bootstrapped

### Details

`rgraph` is a reasonably versatile routine for generating random network data. The graphs so generated are either Bernoulli graphs (graphs in which each edge is a Bernoulli trial, independent conditional on the Bernoulli parameters), or are bootstrapped from a user-provided edge distribution (very handy for CUG tests). In the latter case, edge data should be provided using the `tielist` argument; the exact form taken by the data is irrelevant, so long as it can be coerced to a vector. In the former case, Bernoulli graph probabilities are set by the `tprob` argument as follows:

1. If `tprob` contains a single number, this number is used as the probability of all edges.
2. If `tprob` contains a vector, each entry is assumed to correspond to a separate graph (in order). Thus, each entry is used as the probability of all edges within its corresponding graph.
3. If `tprob` contains a matrix, then each entry is assumed to correspond to a separate edge. Thus, each entry is used as the probability of its associated edge in each graph which is generated.
4. Finally, if `tprob` contains a three-dimensional array, then each entry is assumed to correspond to a particular edge in a particular graph, and is used as the associated probability parameter.

Finally, note that `rgraph` will symmetrize all generated networks if `mode` is set to ``graph'' by copying down the upper triangle. The lower half of `tprob`, where applicable, must still be specified, however.

### Value

A graph stack

### Author(s)

Carter T. Butts buttsc@uci.edu

### References

Erd"{o}s, P. and R'{e}nyi, A. (1960). ``On the Evolution of Random Graphs.'' Public Mathematical Institute of Hungary Academy of Sciences, 5:17-61.

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

### See Also

`rmperm`, `rgnm`, `rguman`

### Examples

    #Generate three graphs with different densities
    g<-rgraph(10,3,tprob=c(0.1,0.9,0.5))

    #Generate from a matrix of Bernoulli parameters
    g.p<-matrix(runif(25,0,1),nrow=5)
    g<-rgraph(5,2,tprob=g.p)

[Package sna version 1.1 Index]