Package edu.cmu.tetrad.graph

Class SemGraph

java.lang.Object
edu.cmu.tetrad.graph.SemGraph
All Implemented Interfaces:
Graph, TetradSerializable, Serializable
public final class SemGraph extends Object implements Graph
Represents the graphical structure of a structural equation model. The linear structure of the structural equation model is constructed by adding non-error nodes to the graph and connecting them with directed edges. As this is done, the graph automatically maintains the invariant that endogenous non-error nodes are associated with explicit error nodes in the graph and exogenous non-error nodes are not. An associated error node for a node N is an error node that has N as its only child, E-->N. Error nodes for exogenous nodes are always implicit in the graph. So as nodes become endogenous, error nodes are added for them, and as they become exogenous, error nodes are removed for them. Correlated errors are represented using directed edges among exogenous nodes. Directed edges may therefore be added among any exogenous nodes in the graph, though the easiest way to add (or remove) exogenous nodes is to determine which non-exogenous nodes N1, N2 they are representing correlated errors for and then to use this formulation: 
     addBidirectedEdge(getExogenous(node1), getExogenous(node2));
     removeEdge(getExogenous(node1), getExogenous(node2));
This avoids the problem of not knowing whether the exogenous node for a node is itself or its associated error node.
Version:
$Id: $Id
Author:
josephramsey
See Also: