Calculates the number of different directed acyclic graphs
for a set of discrete and continuous nodes.
Usage
numbermixed(nd,nc)
Arguments
nd
an integer, which gives the number of discrete nodes.
nc
an integer, which gives the number of continuous nodes.
Value
A numeric containing the number of directed acyclic graphs with the given node
configuration.
Details
No arrows are allowed from continuous nodes to discrete nodes. Cycles
are not allowed. The
number of networks is given by B�ttcher (2003), using the result in
Robinson (1977).
When nd+nc>15, the procedure is quite slow.
References
B�ttcher, S.G. (2003). Learning Conditional Gaussian
Networks. http://www.math.auc.dk/~alma. Aalborg University, 2003.
Robinson, R.W. (1977). Counting unlabeled acyclic digraphs, {\emLecture
Notes in Mathematics}, 622: Combinatorial Mathematics.
Further information about deal can be found at:
http://www.math.auc.dk/novo/deal.