hg.frequent_itemsets#

Frequent-itemset mining, augmented so each transaction can carry a numeric value that is accumulated alongside the item count (support).

This lets you mine itemsets weighted by an arbitrary per-transaction quantity (revenue, duration, …) in addition to plain co-occurrence support. Pass no transaction_values to get ordinary (count-only) frequent-itemset mining.

The implementation is Eclat (depth-first search over item tidlists — the sets of transaction indices an item appears in), which is both correct and simple: an itemset’s support is the size of the intersection of its items’ tidlists, and its accumulated value is the sum of those transactions’ values.

(Earlier versions of this module vendored an FP-growth fork whose conditional tree was subtly wrong; this Eclat implementation replaces it and is verified against a brute-force reference.)

Functions

find_frequent_itemsets(transactions, *[, ...])

Find frequent itemsets in transactions, yielded as FrequentItemset ((items, support, value)).

Classes

FrequentItemset(items, support, value)

A frequent itemset result.

class hg.frequent_itemsets.FrequentItemset(items, support, value)[source]#

Bases: NamedTuple

A frequent itemset result.

Tuple-unpackable as (items, support, value):

items: the items making up the itemset (a list).
support: number of transactions containing the itemset (the count).
value: the accumulated per-transaction value over those transactions (equals support when no transaction_values were supplied).

items: list#: Alias for field number 0

support: int#: Alias for field number 1

value: float#: Alias for field number 2

hg.frequent_itemsets.find_frequent_itemsets(transactions, *, transaction_values=None, minimum_support=2)[source]#

Find frequent itemsets in transactions, yielded as FrequentItemset ((items, support, value)).

transactions is any iterable of iterables of hashable items. transaction_values is an optional parallel sequence of numeric weights (one per transaction); when omitted, every transaction has weight 1 so value equals support (ordinary frequent-itemset mining). minimum_support is the minimum number of occurrences for an itemset to be reported.

>>> transactions = [
...     ['bread', 'milk'],
...     ['bread', 'milk', 'eggs'],
...     ['milk', 'eggs'],
...     ['bread', 'butter'],
... ]
>>> for itemset in sorted(
...     find_frequent_itemsets(transactions, minimum_support=2),
...     key=lambda it: (-it.support, sorted(it.items)),
... ):
...     print(sorted(itemset.items), itemset.support)
['bread'] 3
['milk'] 3
['bread', 'milk'] 2
['eggs'] 2
['eggs', 'milk'] 2

Pass transaction_values to weight each transaction (here by basket price); the third field accumulates that weight over the matching transactions:

>>> prices = [4.0, 9.0, 5.0, 7.0]
>>> by_value = {
...     tuple(sorted(it.items)): it.value
...     for it in find_frequent_itemsets(
...         transactions, transaction_values=prices, minimum_support=2
...     )
... }
>>> by_value[('bread', 'milk')]  # baskets 0 (4.0) and 1 (9.0)
13.0