gRbase (version 1.7-5)

rip: Create RIP ordering of the cliques of an undirected graph; create junction tree.

Description

A RIP (running intersection property) ordering of the cliques is also called a perfect ordering. If the graph is not chordal, then no such ordering exists.

Usage

rip(object, root = NULL, nLevels = NULL)
"rip"(object, root = NULL, nLevels = NULL)

ripMAT(amat, root = NULL, nLevels = rep(2, ncol(amat)))
jTree(object, ...)
"jTree"(object, nLevels=NULL, ...)

jTreeMAT(amat, nLevels=rep(2,ncol(amat)), ...)

Arguments

object

An undirected graph represented either as a graphNEL object, an igraph, a (dense) matrix, a (sparse) dgCMatrix.

root

A vector of variables. The first variable in the perfect ordering will be the first variable on 'root'. The ordering of the variables given in 'root' will be followed as far as possible.

nLevels

Typically, the number of levels of the variables (nodes) when these are discrete. Used in determining the triangulation using a "minimum clique weight heuristic". See section 'details'.

amat

Adjacency matrix

...

Additional arguments; currently not used

Value

rip returns a list (an object of class ripOrder. A print method exists for such objects.)

Details

The RIP ordering of the cliques of a decomposable (i.e. chordal) graph is obtained by first ordering the variables linearly with maximum cardinality search (by mcs). The root argument is transfered to mcs as a way of controlling which clique will be the first in the RIP ordering.

The jTree() (and jTree()) (for "junction tree") is just a wrapper for a call of triangulate() followed by a call of rip().

See Also

mcs triangulate moralize ug, dag

Examples

## graphNEL
uG <- ug(~me:ve + me:al + ve:al + al:an + al:st + an:st)
mcs(uG)
rip(uG)
jTree(uG)

## Adjacency matrix
uG <- ug(~me:ve:al + al:an:st, result="matrix")
mcs(uG)
rip(uG)
jTree(uG)

## Sparse adjacency matrix
uG <- ug(c("me","ve","al"),c("al","an","st"), result="Matrix")
mcs(uG)
rip(uG)
jTree(uG)

## Non--decomposable graph
uG <- ug(~1:2+2:3+3:4+4:5+5:1)
mcs(uG)
rip(uG)
jTree(uG)