: ▁ ▁We ▁will ▁use ▁Ap ri ori ▁to ▁determine ▁the ▁frequent ▁item ▁sets ▁of ▁this ▁database . ▁To ▁do ▁this , ▁we ▁will ▁say ▁that ▁an ▁item ▁set ▁is ▁frequent ▁if ▁it ▁appears ▁in ▁at ▁least ▁ 3 ▁transactions ▁of ▁the ▁database : ▁the ▁value ▁ 3 ▁is ▁the ▁support ▁threshold . ▁ ▁The ▁first ▁step ▁of ▁Ap ri ori ▁is ▁to ▁count ▁up ▁the ▁number ▁of ▁occurr ences , ▁called ▁the ▁support , ▁of ▁each ▁member ▁item ▁separately . ▁By ▁sc anning ▁the ▁database ▁for ▁the ▁first ▁time , ▁we ▁obtain ▁the ▁following ▁result ▁ ▁All ▁the ▁item sets ▁of ▁size ▁ 1 ▁have ▁a ▁support ▁of ▁at ▁least ▁ 3 , ▁so ▁they ▁are ▁all ▁frequent . ▁ ▁The ▁next ▁step ▁is ▁to ▁generate ▁a ▁list ▁of ▁all ▁pairs ▁of ▁the ▁frequent ▁items . ▁ ▁For ▁example , ▁regarding ▁the ▁pair ▁{ 1 , 2 }: ▁the ▁first ▁table ▁of ▁Example ▁ 2 ▁shows ▁items ▁ 1 ▁and ▁ 2 ▁appearing ▁together ▁in ▁three ▁of ▁the ▁item sets ; ▁therefore , ▁we ▁say ▁item ▁{ 1 , 2 } ▁has ▁support ▁of ▁three . ▁ ▁The ▁pairs ▁{ 1 , 2 }, ▁{ 2 , 3 }, ▁{ 2 , 4 }, ▁and ▁{ 3 , 4 } ▁all ▁meet ▁or ▁exceed ▁the ▁minimum ▁support ▁of ▁ 3 , ▁so ▁they ▁are ▁frequent . ▁The ▁pairs ▁{ 1 , 3 } ▁and ▁{ 1 , 4 } ▁are ▁not . ▁Now , ▁because ▁{ 1 , 3 } ▁and ▁{