mathgraph (version 0.9-14)

incidmat: Incidence Matrix for a Mathematical Graph

Description

Returns an object of class "incidmat" which is a matrix indicating the start and end node for each edge in the graph.

Usage

incidmat(x, …)
# S3 method for mathgraph
incidmat(x, expand=TRUE, general=FALSE, …)
is.incidmat(x)

Arguments

x

object representing a mathematical graph.

expand

logical flag: if TRUE, then undirected edges are represented by two columns in the output. If FALSE, then both non-zero elements of an undirected edge are positive.

general

logical flag: if TRUE, then there is a non-zero entry in a column representing a loop.

…

generic arguments.

Value

an object of class "incidmat" which is a matrix with rows representing nodes and columns representing edges. Generally speaking, there is a 1 in the location where an edge begins and a -1 in the location where it ends. Frank Harary defines incidence matrix with expand = FALSE.

Details

The incidmat function is generic, with a method for class "mathgraph".

is.incidmat is the membership function for this class.

References

Chachra, V., Ghare, P. M. and Moore, J. M. (1979). Applications of Graph Theory Algorithms. Elvesier North Holland, New York.

Harary, Frank (1969). Graph Theory, p. 160. Addison Wesley.

See Also

adjamat, mathgraph, getpath.incidmat

Examples

# NOT RUN {
incidmat(mathgraph(~ 1:3 / 3:5, dir=TRUE))
incidmat(mathgraph(~ 1:3 / 3:5, dir=FALSE))
incidmat(mathgraph(~ 1:3 / 3:5, dir=FALSE), expand=FALSE)

# }