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Returns an object of class "incidmat"
which is a matrix indicating
the start and end node for each edge in the graph.
incidmat(x, …)
# S3 method for mathgraph
incidmat(x, expand=TRUE, general=FALSE, …)is.incidmat(x)
object representing a mathematical graph.
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.
logical flag: if TRUE
, then there is a non-zero
entry in a column representing a loop.
generic arguments.
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
.
The incidmat
function is generic, with a method for
class "mathgraph"
.
is.incidmat
is the membership function for this class.
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.
# 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)
# }
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