about input data

[frankwhzhang]

hi, i have a question about input data. if user1 buys {item1,item2} at t1 , and buys {item3,item4} at t2 . input data is: % user1 item1 item3, % user1 item1 item4 , % user1 item2 item3 , % user1 item2 item4. in total 4 records .