If year=1,2,3,4; and prov=1,2,3,4,5,6,7. So how to calculate i*j, thanks a lot!
I run this，but it is wrong.
forvalues i=1/4 {
forvalues j=1/7 {
gen yearprov `i' `j'=year`i'*prov`j'
}
}