ugraph {graph} | R Documentation

## Underlying Graph

### Description

For a directed graph the underlying graph is the graph that is constructed where all edge orientation is ignored. This function carries out such a transformation on `graphNEL` instances.

### Usage

    ugraph(graph)

### Arguments

`graph` | a `graph` object.

### Details

If `graph` is already undirected then it is simply returned.

If `graph` is a multi-graph (has multiple edges) an error is thrown as it is unclear how to compute the underlying graph in that context.

The method will work for any `graph` subclass for which an `edgeMatrix` method exists.

### Value

An instance of `graphNEL` with the same nodes as the input but which is `undirected`.

### Author(s)

R. Gentleman

### References

Graph Theory and its Applications, J. Gross and J. Yellen.

### See Also

`connComp` `edgeMatrix`

### Examples

    V <- letters[1:4]
    edL2 <- vector("list", length=4)
    names(edL2) <- V
    for(i in 1:4)
      edL2[[i]] <- list(edges=c(2,1,2,1)[i], weights=sqrt(i))
    gR2 <- graphNEL(nodes=V, edgeL=edL2, edgemode="directed")

    ugraph(gR2)

[Package graph version 1.62.0 Index]