PnodeEvidence: Gets or sets the value of a Pnode.

In ralmond/PNetica: Parameterized Bayesian Networks Netica Interface

Gets or sets the value of a Pnode.

Description

Adding evidence to a Bayesian network is done by setting the value of the node to one of its states. The generic function Peanut::PnodeEvidence (and the method for a NeticaNode) simply returns the to which it is set, or NA if the node is not set. There are a number of different ways of setting the state depending on the type of the value argument (see Details).

Usage

## S4 method for signature 'NeticaNode'
PnodeEvidence(node)
## S4 replacement method for signature 'NeticaNode,ANY'
PnodeEvidence(node) <- value

Arguments

node	A NeticaNode object whose value is to be set.
value	A value representing the new type of the argument. See details.

Details

The generic function PnodeEvidence is defined in the Peanut package. It returns either the name of a state (discrete node), a numeric value (continuous node) or NA if the node has not been set.

There are different methods for different classes for the value argument (the RHS of the assignment operator).

ANY

If no other method is appropriate, does nothing and issues a warning.

NULL

The value of the node is retracted (RetractNodeFinding).

character

If the value is the name of a state, then the node will be set to that state (NodeFinding). Otherwise, nothing will be done and a warning will be issued.

factor

The character value of the value is uses (see character method).

logical

This method assumes that the node has exactly two states, and that those states have values (PnodeStateValues, NodeLevels) 0 and 1. These levels are used to determine the mapping of TRUE and FALSE to states. If node state values are not set, then the character method is called using “TRUE” or “FALSE” as the value.

numeric

If the value is of length 1, then the value of the node is set (NodeValue) to the argument. If the value is a vector of the same length as the number of states of the node, then it is regarded as virtual evidence, and the likelihood is set (NodeLikelihood).

difftime

Difftime values are converted to real numbers in seconds, then the node value is set (see numeric method).

Value

PnodeEvidence: For all node types, if the node is not set, PnodeEvidence returns NA.

If the node is continuous, its currently set value is returned as a numeric scalar (NA if not set).

If the node is discrete, usually a character value giving the current state (or NA) is returned. However, if the node was assigned a likelihood instead of exact evidence, the likelihood vector is returned.

PnodeEvidence<- returns the node argument invisibly.

Note

For continuous nodes, PnodeEvidence is equivalent to NodeValue. For discrete nodes, it maps to either NodeFinding or NodeLikelihood

Author(s)

Russell Almond

See Also

The function PnetCompile usually needs to be run before this function has meaning.

The functions PnodeStates and PnodeStateBounds define the legal values for the value argument.

Examples

sess <- NeticaSession()
startSession(sess)

irt10.base <- ReadNetworks(system.file("testnets","IRT10.2PL.base.dne",
                           package="PNetica"),session=sess)
irt10.base <- as.Pnet(irt10.base)  ## Flag as Pnet, fields already set.
irt10.theta <- PnetFindNode(irt10.base,"theta")
irt10.items <- PnetPnodes(irt10.base)
## Flag items as Pnodes
for (i in 1:length(irt10.items)) {
  irt10.items[[i]] <- as.Pnode(irt10.items[[i]])
  
}

BuildAllTables(irt10.base)
PnetCompile(irt10.base) ## Netica requirement

stopifnot (is.na(PnodeEvidence(irt10.items[[1]])))

PnodeEvidence(irt10.items[[1]]) <- "Correct"
stopifnot(PnodeEvidence(irt10.items[[1]])=="Correct")

PnodeEvidence(irt10.items[[1]]) <- NULL
stopifnot (is.na(PnodeEvidence(irt10.items[[1]])))

PnodeEvidence(irt10.items[[1]]) <- c(Correct=.6,Incorrect=.3)
stopifnot(all.equal(PnodeEvidence(irt10.items[[1]]),
                    c(Correct=.6,Incorrect=.3),
                    tol=3*sqrt(.Machine$double.eps) ))

foo <- NewContinuousNode(irt10.base,"foo")

stopifnot(is.na(PnodeEvidence(foo)))

PnodeEvidence(foo) <- 1
stopifnot(PnodeEvidence(foo)==1)

DeleteNetwork(irt10.base)
stopSession(sess)

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