Running a loop through variables and through files

[Alberto Basantes]

Can anyone think a way in which I can run a loop through values and through files?

My case:

I have quarterly surveys in a folder.
I need to create a birth cohort variable in each survey as: year-age.

The main problems are two:

1. I can not come up with a way in which in each file a different 'year' is used (i.e in 2007 survey 'year' should be 2007 in 2008 survey 'year' should be 2008)
2. Even having a way to do that, I need a way in which in all the four quarters of the same year the variable 'year' does not change.

I do not have a variable in the survey which indicates the year in which it was conducted (which simplifies considerably the problem)

Thanks in advance

[Roberto Ferrer]

What's the structure of file names? Something must indicate the temporal dimension of the surveys (or not?).

[Alberto Basantes]

Regarding to the filenames, it does indicate the time. The names are e.g. per20071 per20072 per20073 per20074 per20081... per20134

[Kieran McCaul]

Yes, if the file name's contain the "year" and the "quarter", you can exploit that in a loop.

[Roberto Ferrer]

Then use the relevant parts of the filenames to construct your loop. See -fs- by Nick Cox from SSC which is a convenience command to list file names in a directory. See also -help string functions- to manipulate strings. The last character of your file name indicates the quarter and the four before that the year. That should be enough, if I understand the problem correctly. (I'd like to give an example but I'm writing from a clunky mobile device.)

[Roberto Ferrer]

If you know the years then a simple -forvalues - should be enough.

[Alberto Basantes]

Thank you very much, I solved it in this way:


(Part code, not for running) local files : dir "`c(pwd)'" files "*.dta"
fs *.dta

foreach file in `files' {
use `file', clear
local file_name = "`file'"
drop year cohort
gen year=substr("`file_name'", 9 , 4 )
destring(year),replace

capture confirm variable edad
if !_rc {
gen cohort=year-edad
}
else {
gen cohort=year-p03
}
local i=`i'+1
cd ".."
save, replace
}
(End of part code)

Probably not the most efficient way, but it worked.
Thanks again.