30 Chapter 2 assoCiation rules
transaction. An association is an implication of the form X ⇒ Y, where X, Y
⊆ Z, and X ∩ Y = ∅. Two factors affect the significance of association rules:
support and confidence. We say that the rule X ⇒ Y has support s in the trans-
action set D if s% of the transactions in D contain X ∪ Y. On the other hand,
we say that the rule X ⇒ Y holds in the transaction set D with confidence c if
c % of the transactions in D that contain X also contain Y.
Given a set of transactions D, the problem of mining association rules is
to generate all association rules that have support and confidence greater
than a minimum support (called minsup) and a minimum confidence (called
minconf ), respectively. Both minsup and ...