Important Details of Apriori a How to generate candidates? Step 1: self-joining Lk Step 2: pruning How to count supports of candidates? Example of Candidate-generation L3abc abd, acd, ace, bcdy Self-joining: L3 L abcd from abc and abd adde from add and ace Pruning: acde is removed because ade is not in L3 Abcd February 4, 2021 Data Mining: Concepts and Techniques 14February 4, 2021 Data Mining: Concepts and Techniques 14 Important Details of Apriori ◼ How to generate candidates? ◼ Step 1: self-joining Lk ◼ Step 2: pruning ◼ How to count supports of candidates? ◼ Example of Candidate-generation ◼ L3={abc, abd, acd, ace, bcd} ◼ Self-joining: L3*L3 ◼ abcd from abc and abd ◼ acde from acd and ace ◼ Pruning: ◼ acde is removed because ade is not in L3 ◼ C4={abcd}