Katsuhide Isa wrote
> Hello,
>
> I'm trying to merge a collection of dta files and create
> new time-variables at the same time.
> Specifically, I'd like to execute the following two routines
> simultaneously:
>
> ----------routine 1----------
> foreach file in personnel_1997 personnel_1998 personnel_1999
> personnel_2000 personnel_2001 {
> use "`file'"
> sort id
> save "`file'", replace
> use personnel /*master file*/
> sort id
> capture confirm variable _merge
> if _rc {
> continue
> }
> else {
> drop _merge
> }
> merge id using "`file'"
> save personnel, replace
> }
>
> ----------routine 2----------
> forvalues i = 1997/2001 {gen year`i' = `i''}
>
> ----------
>
> Is it possible to execute the above two routines
> combining -foreach- and -forvalues- simultaneously?
> For now, as I don't have a good idea, I repeatedly
> use the following simple routine as for routine 2:
>
> ----------routine 2'----------
> use personnel_1997, clear
> gen year1997 = 1997
> save personnel_1997_temp, replace
> (and so on)
>
> ----------
How about:
-----------------------------------
forvalues i = 1997/2001 {
use "personnel_`i'"
sort id
gen year = `i'
save "using", replace
use personnel
sort id
capture drop _merge
merge id using "using""
save personnel, replace
}
erase "using.dta"
--------------------------------------
This combines your two loops and simplifies the code. Note that this
generates only one variable for year, as this stores the same information and
saves some bandwith. Moreover I store the using data temporarily with a
different filename. This keeps your original data as it is, which is
necassary if you want to rerun the code.
Personally I prefer doing this in two loops. In this case it is not necassary
to reload the master file over and over again:
------------------------------------------
* Prepare using data
forvalues i = 1997/2001 {
use "personnel_`i'"
sort id
gen year = `i'
save "using_`i', replace
}
* Load Master Data
use personnel
sort id
* Merge Data
forvalues i = 1997/2001 {
merge id using "using_`i'"
drop _merge
erase using_`i'.dta /* Clean up things */
}
save personnel_new, replace
------------------------------------------------
Finally you might want to check out -mmerge- on SSC which makes merging much
easier.
hope this helps
uli
--
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