Apriori Algorithm - Algorithm Pseudocode

Algorithm Pseudocode

The pseudocode for the algorithm is given below for a transaction database, and a support threshold of . Usual set theoretic notation is employed, though note that is a multiset. is the candidate set for level . Generate algorithm is assumed to generate the candidate sets from the large itemsets of the preceding level, heeding the downward closure lemma. accesses a field of the data structure that represents candidate set, which is initially assumed to be zero. Many details are omitted below, usually the most important part of the implementation is the data structure used for storing the candidate sets, and counting their frequencies.

Apriori large 1-itemsets while for transactions for candidates return