st: superposed rolled windows

["irodriguez" <irodriguez@utdt.edu>]

statalisters

i need to generate some columns data in excel I think I could calculate them in stata

I have a panel data with firms, and profits for the period 1990/2004 No all the firms have the same period of data

I need to calculate others 4 columns for profit

superposing a rolling period window of 3 periods.

Example:

original data base

Firms    Years   Profits   

firm 1     1990     7

firm 1      1991     9

firm 1      1992      2

firm 1      1993       6

firm 1       1994      5    

firm 1       1995     4

firm 2      1990      3

firm 2      1991      2

firm 2      1992      1

firm 2       1993     3

...

 

New data base

Firms    Years   Profits1    Profit2   Profit3   

firm 1     1990     7                9         2

firm 1      1991     9               2         6

firm 1      1992      2              6         5

firm 1      1993       6            5          4

firm 2      1990      3             2           1

firm 2      1991      2              1          3

                                         

How can I do it

Thanks