How do I know the "support" of each association rules in Weka?

Question

I am using Apriori algorithem in Weka for association rule mining. I know that support for each rule is equal to (occurnce / total-rules ). Weka gave me the number of occurnce. But how do I know the number of rules?

Answer 1

Seems to be some confusion in the definitions.

Consider an association rule X --> Y and T a set of n transactions.

The support for X --> Y is defined to be the fraction of transaction T that satisfy the union of items X and Y. (X U Y).count/n

APRIORI algorithm, in Weka, returns the result as a collection of rules of this kind: antecedent <support> -> Consequence <confidence>, so you already have the value of support.

However if you need the number of rules, for something else, there is one parameters of the algorithm and also in the output the rules are numbered.