NetworkFootprint {RNetica}R Documentation

Returns a list of names of unconnected edges.

Description

When a link is detached through setting a NodeParents() to NULL, or through copying a node but not its parent to a new network, this leaves a stub node, an unsatisfied connection. This function runs through the set of nodes in a network and lists the names of all unsatisfied connections.

Usage

NetworkFootprint(net)

Arguments

net

An active NeticaBN to be examined.

Details

Stub nodes – unsatisfied links or connections – can happen in two ways. Either by setting one of the values of NodeParents(node) to NULL, or by copying a node (using CopyNodes()) without copying its parents. (This can also be done in the Netica GUI by detaching the link from the parent end). This this case Netica names the NodeInputNames() according to the name of the old node.

The function NetworkFootprint(net) search all of the nodes in net to find stub nodes, and reports the NodeInputNames() of the stub nodes. This function provides a test for unsatisfied connections, and should be of assistance when joining two networks together. The function AdjoinNetwork(sm,em) joins two networks together and attempts to resolve the unsatisfied connections in em.

One particular application of the footprint is in the EM–SM algorithm (Almond et al, 1999; Almond and Mislevy, 1999). Here it is assumed that nodes in the footprint of an evidence model will be joined. Making a clique node MakeCliqueNode() ensures that joint information from the evidence model will find a good home in the system model network.

Value

A character vector giving the input names of the stub nodes in net. Duplicate values are removed.

Author(s)

Russell Almond

References

Almond, R. G. & Mislevy, R. J. (1999) Graphical models and computerized adaptive testing. Applied Psychological Measurement, 23, 223-238.

Almond, R., Herskovits, E., Mislevy, R. J., & Steinberg, L. S. (1999). Transfer of information between system and evidence models. In Artificial Intelligence and Statistics 99, Proceedings (pp. 181–186). Morgan-Kaufman

See Also

NeticaNode, NodeParents(), MakeCliqueNode(), NodeInputNames(), CopyNodes(),AdjoinNetwork()

Examples

sess <- NeticaSession()
startSession(sess)

## System/Student model
EMSMSystem <- ReadNetworks(file.path(library(help="RNetica")$path,
                           "sampleNets","System.dne"), session=sess)

CompileNetwork(EMSMSystem)
JunctionTreeReport(EMSMSystem)

## Evidence model for Task 1a
EMTask1a <- ReadNetworks(file.path(library(help="RNetica")$path,
                           "sampleNets","EMTask1a.dne"), session=sess)

NetworkFootprint(EMTask1a)
## The corresponding clique is not in system model, so force it in.
MakeCliqueNode(NetworkFindNode(EMSMSystem, NetworkFootprint(EMTask1a)))
CompileNetwork(EMSMSystem)
JunctionTreeReport(EMSMSystem)


## Evidence model for Task 2a
EMTask2a <- ReadNetworks(file.path(library(help="RNetica")$path,
                           "sampleNets","EMTask2a.dne"), session=sess)
NetworkFootprint(EMTask2a)
## This is already a clique, so nothing to do.

DeleteNetwork(list(EMSMSystem,EMTask1a,EMTask2a))
stopSession(sess)


[Package RNetica version 0.7-1 Index]