DDGraph-dash-class: Direct Dependence Graph class...
In ddgraph: Distinguish direct and indirect interactions with Graphical Modelling

Direct Dependence Graph class

`dataset`	the DDDataSet object used to make the DDGraph
`params`	the parameters used in making the DDGraph
`stats`	the values of statistics used to make the DDGraph
`direct`	the list of indicies of direct variables
`indirect`	the list of indicies of indirect variables
`joint`	the list of indicies of joint variables
`conditional`	the list of indicies of conditional variables
`conditionalJoint`	the list of indicies of conditionally joint variables
`edges`	the list of edges (type DDGraphEdge) the describe the graph

This class represents one Direct Dependence Graphs (generated by a certain conditional independence test, alpha value, etc). It contains the original DDDataSet object from which it stems, the set of parameters, the set of informative statistics as well as lists of direct, joint and indirect variables. Finally, it contains the edges needed to draw the graph.

initialize: signature(.Object = "DDGraph"): Construct new DDGraph object
names: signature(x = "DDGraph"): Names of different properties that can be accessed with $ operator
$: signature(x = "DDGraph"): access a property by name
show: signature(object = "DDGraph"): show method for DDGraph
plot: signature(x = "DDGraph", y = "missing"): Plot DDGraphs using RGraphviz