Description Usage Arguments Details Value Note Author(s) See Also Examples

For our purposes an *edge matrix* is a matrix with two rows and as
many columns as there are edges. The entries in the first row are the
index of the node the edge is *from*, those in the second row indicate
the node the edge is *to*.

If the graph is “undirected” then the `duplicates`

option
can be used to indicate whether reciprocal edges are wanted. The
default is to leave them out. In this case the notions of *from*
and *to* are not relevant.

1 2 3 4 | ```
edgeMatrix(object, duplicates=FALSE)
eWV(g, eM, sep = ifelse(edgemode(g) == "directed", "->",
"--"), useNNames=FALSE)
pathWeights(g, p, eM=NULL)
``` |

`object` |
An object that inherits from |

`g` |
An object that inherits from |

`duplicates` |
Whether or not duplicate edges should be produced for “undirected” graphs. |

`eM` |
An edge matrix |

`sep` |
a character string to concatenate node labels in the edge label |

`useNNames` |
a logical; if TRUE, node names are used in the edge label; if FALSE, node indices are used |

`p` |
a vector of node names constituting a path in graph |

Implementations for `graphNEL`

, `clusterGraph`

and
`distGraph`

are available.

`edgeMatrix`

returns a matrix with two rows, *from* and *to*, and as many columns
as there are edges. Entries indicate the index in the node vector that
corresponds to the appropriate end of the edge.

`eWV`

uses the edge matrix to create an annotated vector of
edge weights.

`pathWeights`

returns an annotated vector of edge weights
for a specified path in a graph.

A path through an undirected graph may have several representations as a named vector of edges. Thus in the example, when the weights for path b-a-i are requested, the result is the pair of weights for edges a–b and a–i, as these are the edge labels computed for graph g1.

R. Gentleman

1 2 3 4 5 6 7 8 | ```
set.seed(123)
g1 <- randomGraph(letters[1:10], 1:4, p=.3)
edgeMatrix(g1)
g2 <- new("clusterGraph", clusters=list(a=c(1,2,3), b=c(4,5,6)))
em2 <- edgeMatrix(g2)
eWV(g1, edgeMatrix(g1))
eWV(g1, edgeMatrix(g1), useNNames=TRUE)
pathWeights(g1, c("b", "a", "i"))
``` |

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