extract.formulas.R

extract.formula<-function(formu){
	if (!is(formu,"formula"))
		stop("X should be a valid formula of form \n y ~ x1 + x2 | conditional")
	resp <- formu[[2]]
	if( length(formu[[3]]) < 2 ){ formu <- formu }else{ formu <- formu[[3]] }
	
	flattener <- function(f) {if (length(f)<3) return(f);
	                            c(Recall(f[[2]]),Recall(f[[3]]))}

	if (formu[[1]] == '|'){
		condi 	<- formu[[3]]
		vars 	<- flattener(formu[[2]])
	}else if(formu[[1]] == '+' & length(formu) < 4){
		condi 	<- NA
		vars 	<- c(formu[[2]], formu[[3]])
	}else if(length(formu[[3]]) < 2){
		condi 	<- NA
		vars 	<- formu[[3]]
	}

	list(resp=resp,condi=condi,vars=vars)
}