graph-create function

Create undirected and directed graphs

These functions are wrappers for creation of graphs as primarily igraph objects but also as adjacency matrices

ug(..., result = "igraph")

ugi(...)

ugList(x, result = "igraph")

dag(..., result = "igraph", forceCheck = FALSE)

dagi(..., forceCheck = FALSE)

dagList(x, result = "igraph", forceCheck = FALSE)

Arguments

• ...: A generating class for a graph, see examples below

• result: The format of the graph. The possible choices are "igraph" (for an igraph

  object), "matrix" (for an adjacency matrix), "dgCMatrix" (for a sparse matrix).

• x: A list or individual components from which a graph can be created.

• forceCheck: Logical determining if it should be checked if the graph is acyclical. Yes, one can specify graphs with cycles using the dag() function.

Returns

Functions ug(), and dag() can return a an igraph object, a sparse or a dense adjacency matrix.

Examples

## The following specifications of undirected graphs are equivalent:
uG1 <- ug(~ a:b:c + c:d)
uG2 <- ug(c("a", "b", "c"), c("c", "d"))
uG3 <- ug(c("a", "b"), c("a", "c"), c("b", "c"), c("c", "d"))

## The following specifications of directed acyclig graphs are equivalent:
daG1 <- dag(~ a:b:c + b:c + c:d)
daG2 <- dag(c("a", "b", "c"), c("b", "c"), c("c", "d"))

## dag() allows to specify directed graphs with cycles:
daG4 <- dag(~ a:b + b:c + c:a) # A directed graph but with cycles

## A check for acyclicity can be done with
## daG5 <- dag(~ a:b + b:c + c:a, forceCheck=TRUE) 

## A check for acyclicity is provided by topoSort
topo_sort( daG2 )
topo_sort( daG4 )

## Different representations
uG7 <- ug(~a:b:c + c:d, result="igraph")    # igraph
uG8 <- ug(~a:b:c + c:d, result="matrix")    # dense matrix
uG9 <- ug(~a:b:c + c:d, result="dgCMatrix") # sparse matrix

Author(s)

Søren Højsgaard, sorenh@math.aau.dk