Tree Graphical Model

The FactorGraph supports the composite type DiscreteTreeModel based on the forward–backward message passing schedule, with three fields:

• DiscreteTreeGraph;
• DiscreteInference;
• DiscreteSystem.

The subtype DiscreteTreeGraph describes the tree factor graph obtained based on the input data. The BP inference and marginal values are kept in the subtype DiscreteInference. The input system being solved is preserved in the subtype DiscreteSystem. Note that the function discreteTreeModel() returns the main composite type DiscreteTreeModel with all subtypes.

Build graphical model

Input arguments of the function discreteTreeModel() describe the tree graphical model, while the function returns DiscreteTreeModel type.

Loads the system data passing arguments:

bp = discreteTreeModel(probability, table)

Virtual factor nodes

The function discreteTreeModel() receives arguments by keyword to set the message of the virtual factor nodes to initiate messages from leaf variable nodes. This value is applied to all variable nodes and to all their possible states if the corresponding variable node does not have a singly connected factor node.

bp = discreteTreeModel(DATA; message = value)

Default setting of the mean value is message = 1.0.

Root variable node

The function discreteTreeModel() receives argument by keyword to set the root variable node.

bp = discreteTreeModel(DATA; root = index)

Default setting of the root variable node is root = 1.

Tree factor graph

Function checks whether the factor graph has a tree structure.

tree = isTree(gbp)

The tree structure of tha factor graph is marked as tree = true, the opposite is tree = false. The function accepts the composite type DiscreteTreeModel.