Source code for efficient_apriori.apriori

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
High-level implementations of the apriori algorithm.
"""

import typing
from efficient_apriori.itemsets import itemsets_from_transactions
from efficient_apriori.rules import generate_rules_apriori


[docs]def apriori( transactions: typing.Iterable[typing.Union[set, tuple, list]], min_support: float = 0.5, min_confidence: float = 0.5, max_length: int = 8, verbosity: int = 0, output_transaction_ids: bool = False, ): """ The classic apriori algorithm as described in 1994 by Agrawal et al. The Apriori algorithm works in two phases. Phase 1 iterates over the transactions several times to build up itemsets of the desired support level. Phase 2 builds association rules of the desired confidence given the itemsets found in Phase 1. Both of these phases may be correctly implemented by exhausting the search space, i.e. generating every possible itemset and checking it's support. The Apriori prunes the search space efficiently by deciding apriori if an itemset possibly has the desired support, before iterating over the entire dataset and checking. Parameters ---------- transactions : list of transactions (sets/tuples/lists). Each element in the transactions must be hashable. min_support : float The minimum support of the rules returned. The support is frequency of which the items in the rule appear together in the data set. min_confidence : float The minimum confidence of the rules returned. Given a rule X -> Y, the confidence is the probability of Y, given X, i.e. P(Y|X) = conf(X -> Y) max_length : int The maximum length of the itemsets and the rules. verbosity : int The level of detail printing when the algorithm runs. Either 0, 1 or 2. output_transaction_ids : bool If set to true, the output contains the ids of transactions that contain a frequent itemset. The ids are the enumeration of the transactions in the sequence they appear. Examples -------- >>> transactions = [('a', 'b', 'c'), ('a', 'b', 'd'), ('f', 'b', 'g')] >>> itemsets, rules = apriori(transactions, min_confidence=1) >>> rules [{a} -> {b}] """ itemsets, num_trans = itemsets_from_transactions( transactions, min_support, max_length, verbosity, output_transaction_ids=True, ) itemsets_raw = { length: {item: counter.itemset_count for (item, counter) in itemsets.items()} for (length, itemsets) in itemsets.items() } rules = generate_rules_apriori(itemsets_raw, min_confidence, num_trans, verbosity) if output_transaction_ids: return itemsets, list(rules) else: return itemsets_raw, list(rules)
if __name__ == "__main__": import pytest pytest.main(args=[".", "--doctest-modules", "-v"])