Understanding association rules
The result of a market basket analysis is a set of association rules that specify patterns of relationships among items. A typical rule might be expressed in the form:
In plain language, this association rule states that if peanut butter and jelly are purchased, then bread is also likely to be purchased. In other words, "peanut butter and jelly imply bread." Groups of one or more items are surrounded by brackets to indicate that they form a set, or more specifically, an itemset that appears in the data with some regularity. Association rules are learned from subsets of itemsets. For example, the preceding rule was identified from the set of {peanut butter, jelly, bread}.
Developed in the context of Big Data and database science, association rules are not used for prediction, but rather for unsupervised knowledge discovery in large databases, unlike the classification and numeric prediction algorithms presented in previous chapters. Even so, you will find that...
