Generating 2-itemset rules with Arules in R

Question

I'm using Arules library in R to generate rules:

rules = apriori(data = dataset, parameter = list(support = 0.001, confidence = 0.6, minlen=2))

I understand the minlen=2 avoids rules of the form {} => {beer}.

• In arules, is it possible to restrict rules such that LHS and RHS only has a single item? (i.e. Avoiding rules {milk, nappies} => {beer})

• Alternatively, is the rule {milk, nappies} => {beer} equivalent to saying {milk} => {beer} and {nappies} => {beer}?

Any help is appreciated!

Answer 1

I would filter the rules for rules having exactly one item on the LHS.

rules <- rules[sapply(
  1:length(rules)
  ,function(x) length(as(rules@lhs, "list")[[x]])) == 1];

I think, assuming conditional independence of {beer} and {milk}, the rule {milk, nappies} => {beer} is equivalent to saying {nappies} => {beer}, and assuming conditional independence of {beer} and {nappies}, the rule {milk, nappies} => {beer} is equivalent to the rule {milk} => {beer}.