How to generate Candidates Suppose the items in Lk-, are listed in an order Step 1: self-joining Lk-1 insert into CK select p, item p item ay p.itemk-y g itemk-1 from Lk- p, lk-i9 where p item,=g. itemy my pitem -=g. itemk-ypitem- quitemk-1 Step 2: pruning forall itemsets c in Ci do forall (k-1)-subsets s of cdo if (s is not in Lk- then delete cfrom CK February 4, 2021 Data Mining: Concepts and Techniques 15February 4, 2021 Data Mining: Concepts and Techniques 15 How to Generate Candidates? ◼ Suppose the items in Lk-1 are listed in an order ◼ Step 1: self-joining Lk-1 insert into Ck select p.item1 , p.item2 , …, p.itemk-1 , q.itemk-1 from Lk-1 p, Lk-1 q where p.item1=q.item1 , …, p.itemk-2=q.itemk-2 , p.itemk-1 < q.itemk-1 ◼ Step 2: pruning forall itemsets c in Ck do forall (k-1)-subsets s of c do if (s is not in Lk-1 ) then delete c from Ck