Database Reference
In-Depth Information
Customer Number
Items
5
Jam, Soda, Chips, Milk, and Bread
6
Fruit, Soda, Chips, and Milk
7
Peanuts, Soda, Fruit, and Milk
8
Cheese, Peanuts, Yogurt, and Fruit
From a given transaction as above, we will now work to understand if an occurrence
of one item in the table is driven by the presence of any other item in the same trans-
action.
Some of the associations that we can derive are:
•
{Bread} => {Jam}
•
(Soda} => {Chips}
•
{Bread} => {Milk}
These denote implications of the form
X => Y
, where X and Y are
itemsets
.
Let us now get acquainted with some terminology used in the context of association
rules.
•
Itemset
: A collection of one or more items is called an itemset. An example
of an itemset from the preceding table is
{Milk, Bread, Jam}
.
• k-itemset is an itemset that has k items
•
Support
(
s
): Support is the fraction of transactions that contain an itemset.
For example:
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