How to write more efficient loops (forvalues)

[john kinm]

Dear statalist users,

I'm wondering if it's possible to write a more efficient iterator in these three cases.


case 1.

gen making = 20190 if month==1 & year == 2019

forvalues i=2/9 {
replace making = 20190 if month==`i' & year==2019
}

forvalues i=1/9 {
replace making = 20200 if month==`i' & year==2020
}

forvalues i=1/9 {
replace making = 20210 if month==`i' & year==2021
}

forvalues i=1/6 {
replace making = 20220 if month==`i' & year==2022
}

forvalues i=10/12 {
replace making = year if month==`i'
}


case 2.
gen year_month = making*10 + month if month== 1 & year == 2019

forvalues i=2/9 {
replace year_month = making*10 + month if month==`i' & year==2019
}

forvalues i=1/9 {
replace year_month = making*10 + month if month==`i' & year==2020
}

forvalues i=1/9 {
replace year_month = making*10 + month if month==`i' & year==2021
}

forvalues i=1/6 {
replace year_month = making*10 + month if month==`i' & year==2022
}

forvalues i=10/12 {
replace year_month = making*100 + month if month==`i'
}


case 3.

gen quarter = 1 if month == 1 |month == 2| month == 3
replacequarter = 2 if month == 4 |month == 5| month == 6
replacequarter = 3 if month == 7 |month == 8| month == 9
replacequarter = 4 if month == 10|month == 11| month == 12



thank you!

[Clyde Schechter]

None of these cases requires any loop at all.

Case 1 can be done in a few lines of code:

gen making = 10*year
replace making = 10*year if year == 2022 & inrange(month, 1, 6)
replace making = year if inrange(month, 10, 12)

(In fact, these three lines of code can be reduced to a single line of code, but it would be rather opaque, so better to do it in three easy-to-understand lines of code.)

Case 2 is rather similar

gen year_month= 10*making+month if inrange(year, 2019, 2021) & inrange(month, 1, 9)
replace year_month = 10*making_month if year == 2022 & inrange(month, 1, 6)
replace year_month = making*100+month if inrange(month, 10, 12)

Case 3 is a one-liner

gen quarter = ceil(month/3)