madlib/madlib — pull request #196 by aojwang (2012-08-12 11:40:22+00:00)
Title: Generate a readable output rules for Apriori

JIRA: [MADLIB-411](http://jira.madlib.net/browse/MADLIB-411)
The old output wasn't readable, since it use sparse vector to represent the rules and contains some useless columns, such as hash_list, hash_key. As per discussion, for a rule A=>B, where A/B is the itemset, we will use an array to kept the original items in the itemset. For example, for rule i: (a, b) => (c), we will have two columns: one is pre, which stores {a, b}; the other is post, which stores {c}. Details please refer to my comments of the bug.