[Sartaj Hussain]

gen date1=date(month,"DMY")
format date1 %td
drop month
rename date1 date
gen mdate= mofd(date)
format mdate %tm
bysort stock_id (date): gen rt =((pr[_n]-pr[_n-1])/pr[_n-1])
rangestat (max) rt, by(stock_id) interval(mdate -1 -1)
sort mdate
by stock_id mdate: keep if _n == 1
rename rt_max max

I tried above code but for the line

by stock_id mdate: keep if _n == 1

following error surfaces.

not sorted
r(5);

How can i fix this?

[Clyde Schechter]

Change -sort mdate- to -sort stock_id mdate-.

[Sartaj Hussain]

Thanks indeed. I worked fine now.