Practical Predictive Analytics

The sample market basket

Each transaction numbered 1-10 listed previously represents a basket of items purchased by a shopper. These are typically all items that are associated with a particular transaction or invoice. Each basket is enclosed within braces {}, and is referred to as an itemset. An itemset is a group of items that occur together.

Market basket algorithms construct rules in the form of:

Itemset{x1,x2,x3 ...} --> Itemset{y1,y2,y3...}. 

This notation states that buyers who have purchased items on the left-hand side of the formula (lhs) have a propensity to purchase items on the right-hand side (rhs). The association is stated using the à symbol, which can be interpreted as implies.

The lhs of the notation is also known as the ...