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“4137X˙CH04˙Akerkar” — 2007/9/17 — 11:02 — page 163 — #45
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4.4 Association 163
ation rules in which the user is interested. The user can state the constraint to specify which
grouping of items is of his interest.
In this section, we will introduce the reader to the association rules and the a priori
algorithm that can be used to discover such rules.
4.4.1 a priori Algorithm
Suppose that A = {l
1
,l
2
, ...l
m
} is a set of items and T is a set of transactions, where each
transaction t is a set of items. Thus, t is a subset of A.
A transaction t is said to support an item l
i
,ifl
i
is present in t. t is said to support a
subset of items X ⊆ A,ift supports ...