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assocrules: improve performance a bit #5

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15 changes: 7 additions & 8 deletions pymining/assocrules.py
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Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
def mine_assoc_rules(isets, min_support=2, min_confidence=0.5):
rules = []
visited = set()
for key in sorted(isets, key=lambda k: len(k), reverse=True):
for key in sorted(isets, key=len, reverse=True):
support = isets[key]
if support < min_support or len(key) < 2:
continue
Expand All @@ -10,28 +9,28 @@ def mine_assoc_rules(isets, min_support=2, min_confidence=0.5):
left = key.difference([item])
right = frozenset([item])
_mine_assoc_rules(
left, right, support, visited, isets,
left, right, item, support, isets,
min_support, min_confidence, rules)

return rules


def _mine_assoc_rules(
left, right, rule_support, visited, isets, min_support,
left, right, last_item, rule_support, isets, min_support,
min_confidence, rules):
if (left, right) in visited or len(left) < 1:
if not left:
return
else:
visited.add((left, right))

support_a = isets[left]
confidence = float(rule_support) / float(support_a)
if confidence >= min_confidence:
rules.append((left, right, rule_support, confidence))
# We can try to increase right!
for item in left:
if item > last_item: continue
new_left = left.difference([item])
new_right = right.union([item])
_mine_assoc_rules(
new_left, new_right, rule_support, visited, isets,
new_left, new_right, item, rule_support, isets,
min_support, min_confidence, rules)