The function PriorVariable yields the prior distributions for
all situations associated with a particular variable in the event tree.
PriorVariable(ref, alpha.edge)numeric - It indicates the variable.
vector - Dirichlet hyperparameter vector of a situation associated with a particular variable.
a matrix. Each row represents the Dirichlet hyperparameter vector of a situation associated with a particular variable in the event tree.
Prior.distribution and
AlphaEdgeInternal