Hi,
My datasets are like following forms:
Inventorid patentyear firmid
3930988 2000 13928
3930988 2001 13928
3930988 2002 15892
3890212 2001 15892
3890212 2001 15892

I'm trying to compare firmid for the same inventor and generate a variable move = 1 if firmid != firmid in the previous rows. The desired results is as follows. For example, for inventor 3930988, he is regarded as move = 1 when the firmid change (15892 VS 13928).
NOTE that, comparison of the firms only within observations. For example, for inventor 3930988, compare firmid within the first 3 rows. for Inventor 3890212, compare within the last two rows. Many thanks if you could provide any suggestions!

Inventorid patentyear firmid move
3930988 2000 13928 0
3930988 2001 13928 0
3930988 2002 15892 1
3890212 2001 15892 0
3890212 2001 15892 0