I have a dataset that has distinct Ids, purchase dates, and purchase amounts. It is sorted by Id and purchase date. What I want to do is create a field that numbers the purchases in order so we can see how many purchases they've made since their first. For example,
Id Purchase_date Purchase_amount (new field)
001 1/5/11 25.00 1
001 2/6/11 25.00 2
001 8/12/11 16.00 3
001 9/14/11 12.00 4
002 5/20/11 8.00 1
002 8/17/11 20.00 2
002 9/15/11 11.00 3