PnodeParents: Gets or sets the parents of a parameterized node.

In ralmond/Peanut: Parameterized Bayesian Networks, Abstract Classes

Gets or sets the parents of a parameterized node.

Description

A parent of a child node is another node which has a link from the parent to the child. This function returns the list of parents parents of the the node. It allows the list of parents for the node to be set, altering the topology of the network (see details).

Usage

PnodeParents(node)
PnodeParents(node) <- value
PnodeNumParents(node)
PnodeParentNames(node)
PnodeParentStates(node)

Arguments

node	A Pnode object whose parents are of interest.
value	A list of Pnode objects (or NULLs) which will become the new parents. Order of the nodes is important. See details.

Details

At its most basic level, PnodeParents() reports on the topology of a network. Suppose we add the links A1 --> B, A2 --> B, and A3 --> B to the network. Then PnodeParents(B) should return list(A1, A2, A3). The order of the inputs is important, because that this determines the order of the dimensions in the conditional probability table (BuildTable()).

The parent list can be set. This can accomplishes a number of different goals: it can replace a parent variable, it can add additional parents, it can remove extra parents, and it can reorder parents. Changing the parents alters the topology of the network. Note that the network must always be acyclic directed graphs. In particular, if changing the parent structure will result in a directed cycle,it will likely raise an error).

Value

PnodeParents list of Pnode objects representing the parents in the order that they will be used to establish dimensions for the conditional probability table.

The setting variant returns the modified child object.

The expression PnodeNumParents(node) returns an integer scalar giving the number of parents of node.

The expression PnodeParentNames(node) is a shortcut fo sapply(PnodeParents(node), PnodeName) and PnodeParentStates(node) is a shortcut for sapply(PnodeParents(node), PnodeName)

Author(s)

Russell Almond

See Also

Pnode, PnodeParentTvals

Examples

## Not run: 
library(PNetica) ## Requires PNetica
sess <- NeticaSession()
startSession(sess)
abnet <- CreateNetwork("AB", session=sess)

anodes <- NewDiscreteNode(abnet, paste("A",1:3,sep=""))
B <- NewDiscreteNode(abnet,"B")

## Should be empty list
stopifnot(length(PnodeParents(B))==0)

PnodeParents(B) <- anodes
stopifnot(
  length(PnodeParents(B))==3,
  PnodeParents(B)[[2]] == anodes[[2]]
)

## Reorder nodes
PnodeParents(B) <- anodes[c(2:3,1)]
stopifnot(
  length(PnodeParents(B))==3,
  PnodeName(PnodeParents(B)[[2]])=="A3",
  all(nchar(names(PnodeParents(B)))==0)
)

PnodeParentNames(B)
PnodeParentStates(B)

## Remove a node.
PnodeParents(B) <- anodes[2:1]
stopifnot(
  length(PnodeParents(B))==2,
  PnodeName(PnodeParents(B)[[2]])=="A1",
  all(nchar(names(PnodeParents(B)))==0)
)

## Add a node
PnodeParents(B) <- anodes[3:1]
stopifnot(
  length(PnodeParents(B))==3,
  PnodeName(PnodeParents(B)[[3]])=="A1",
  all(nchar(names(PnodeParents(B)))==0)
)

## Remove all parents
PnodeParents(B) <- list()
stopifnot(
  length(PnodeParents(B))==0
)

DeleteNetwork(abnet)
stopSession(sess)

## End(Not run)

ralmond/Peanut documentation built on Sept. 19, 2023, 8:27 a.m.