cd "C:\Users\GagaLee\Desktop\ga"
local ff : dir . files "*.dta"
dis `"`ff'"'

mat ga=J(48,2,.)
local x=1
foreach i of local ff {
use `i'
local N=_N
forvalue a=1(1)`N'{
sum vo2_2 if inrange(_n,`a',(`a'+30))
local xxx=r(sd)/r(mean)
mat ga[`x',1]=`a' if inrange(`xxx',0,0.15)
mat ga[`x',2]=r(mean) if inrange(`xxx',0,0.15)
if inrange(`xxx',0,0.15) break
}
local ++x
}