Hi

i'm doing a 'market model' style event study. I'm looking at the effects of a Fed announcement upon a currency.

As i have no market returns to compute abnormal returns, I will be calculating the theoretical variation in the currency over the preceding 300 days before the event. i will use the mean variation during the estimation window. Theoretical variation (over 300 days, estimation window) = SUM (t=300) [ Variation ]/300.

I have currently undertaken the following steps in preparation for my event study (from do file):
gen ret = ln(px_last[_n+1] / px_last[_n]) destring date, ignore("/") replace gen day_cnt = _n gen target_day = day_cnt if date==20092017 egen max_target_day = max(target_day) gen evday = day_cnt-max_target_day drop day_cnt target_day max_target_day sort evday gen evt_window=1 if evday>=-10 & evday<=10 gen est_window=1 if evday<=302 & evday>=-2
My dataset originally had the exchange rate(px_last) and the date. What commands would i use to compute the daily theoretical variation, and then the mean variation over the 300 day estimation window???

(I'm a stata newbie, but i believe that 'gen window floor (day_cnt/300)' would be a command i may use. but i dont know how to get further.)

Thank you