set.finding {gRaven}

Set, retract and inspect findings

Description

Set, retract and inspect findings

Usage

set.finding(domain, node, finding)
retract(domain, nodes=domain$nodes)
get.finding(domain, nodes=domain$nodes, type = c("entered", "propagated"), 
	namestates=FALSE)

Arguments

domain

name of gRaven domain

node

name of node

nodes

character vector naming one or mode nodes

finding

either a state of node node or a probability distribution over the states, or other non-negative vector of that length.

type

character vector of one or more options to select between evidence entered before or after most recent propagation

namestates

logical, should output have the states labelled

Details

For type, partial matching is used.

Value

For set.finding and retract, a NULL value is invisibly returned. For get.finding, the likelihood vector is invisibly returned for each specified node, in a format governed by namestates. This is a named vector in the case of a single node, otherwise a list of such vectors. For a single node, in the absence of any evidence, a named vectors of 1's is returned.

Differences from RHugin

Findings (or evidence) are handled differently in gRaven (and gRain) than in RHugin, and that is reflected in differences in results from these functions, especially get.finding. For set.finding in gRaven, the case argument is not supported. For get.finding in both packages, previously-set evidence is displayed as a non-negative vector indexed by the states, typically a probability distribution; two enhancements in gRaven are that findings on more than one node can be displayed, and that the format of the output can be controlled by namestates. In gRaven when new evidence is set by set.finding, it replaces any existing evidence on the same node, and all existing evidence on all nodes is "unpropagated". Evidence is held in a data structure cache until propagation, when it is moved to evid; these names are used in labelling the output from get.finding. Finally if no evidence has been entered on a node, RHugin reports a vector of all ones, while gRaven returns such a vector invisibly.

Author(s)

Peter J. Green, [e-mail]

Examples

demo(chest,package="gRaven",echo=FALSE)
chest
set.finding(chest,"asia","yes")
set.finding(chest,"dysp","no")
propagate(chest)

get.belief(chest,"asia")
get.belief(chest,"tub")
get.finding(chest)

retract(chest,"dysp")
get.belief(chest,"tub")
get.finding(chest)