Reducing Number of Candidates Apriori principle If an itemset is frequent then all of its subsets must also be frequent Apriori principle holds due to the following property of the support measure Vx,y:(XcY)→(X)≥(Y) Support of an itemset never exceeds the support of its subsets This is known as the anti-monotone property of support n Steinbach. Kumar Introduction to Data Mining 4/18/2004© Tan,Steinbach, Kumar Introduction to Data Mining 4/18/2004 ‹#› Reducing Number of Candidates Apriori principle: – If an itemset is frequent, then all of its subsets must also be frequent Apriori principle holds due to the following property of the support measure: – Support of an itemset never exceeds the support of its subsets – This is known as the anti-monotone property of support X,Y :(X  Y )  s(X )  s(Y )