R/ftree.bdd.prob(rev1).r

In jto888/FaultTree.BDD.Reference: Reference Implementations of BDD Algorithms on 'ftree' Objects

ftree.bdd.prob<-function(ftree, ft_node=1, bdd=NULL)  {					
					
	if(length(bdd)==0)  {				
	# generate the bdd				
		bdd<-ftree2bdd(ftree, ft_node)			
	# global FT and T1 objects now exist				
	}else{				
	# the ftree object is used to populate basic element probabilities				
	# there is no pre-validation that the elements in the provided bdd 				
	# are present in the ftree object, but a stop is included in bdd.prob				
		FT<-ftree			
	}				
## initialize the table to be used to store probability calculations that need not be repeated					
## the dataframe object is actually a list of matched vectors, but appropriate here					
	T2<<-data.frame(bdd=NULL, ite_prob=NULL, stringsAsFactors=FALSE)				
					
	prob<-bdd.prob(bdd)				
	prob 				
}					
					
					
bdd.prob<-function(bdd)  {					
if(!exists("FT")) stop("FT and a null T2 object are required in global environment")					
					
	if(bdd=="0") {return (0)				
	}else{				
		if(bdd=="1") {return (1)			
		}else{			
			## a table lookup occurs here		
			## with another else block		
					
			ite<-tx2ite(bdd)		
## need to look up the probability for basic element with FT$prob[which( FT$Tag==ite$node)[1]]					
			nodeID<-which( FT$Tag==ite$node)		
			if(length(nodeID)==0) stop(paste0("undefined tag ", ite$node, " in ftree object"))		
			# prob<-FT$PBF[which( FT$Tag==ite$node)[1]]		
			prob<-FT$PBF[nodeID[1]]		
			LHS<-prob*bdd.prob(ite$X1)		
			RHS<-(1-prob) * bdd.prob(ite$X0)		
			ite_prob<-LHS+ RHS		
			## ite_prob<-prob*bdd.prob(as.character(ite$X.1)) + (1-prob) * bdd.prob(as.character(ite$X.0))		
			## add a line to a table of ite_prob calcs		
			T2line<-data.frame(bdd=bdd, ite_prob=ite_prob, stringsAsFactors=FALSE)		
					
			T2<<-rbind(T2, T2line)		
			return(ite_prob)		
		}			
	}				
}