Loop across multiple files

[david jokic]

Hi all,

I am trying to create a loop to run across two different files "PSQ_A" and "PSQ_B".

I want the loop to open each file and run the function 'describe'. I want to then generate a new variable 'Clinic' where the value is 'A' for file "PSQ_A" and 'B' for file "PSQ_B".

I have thought about using command 'forvalues', but I can't seem to get this to work.


Code:

forvalues i=A/B {
use PSQ_`i', clear
describe
gen Clinic=`i'
}

However I get invalid syntax.. Is this the correct command to use over multiple files?

[Nick Cox]

No; it's not. forvalues is for looping over lists of integers of specific form.

help forvalues

This is more likely to work:

foreach i in A  B {
use PSQ_`i', clear
describe
gen Clinic = "`i'"
}

Note that yourgenerate command will fail to do what you want -- it's either illegal or irrelevant, depending. You need the clinic to be a string variable and the double quotes are needed to ensure that.

Detail: describe is a command, not a function. Regardless of terminology elsewhere, that's the Stata terminology.

Detail: in principle, forvalues does support some loops over non-integers, but don't try that until and unless you know how it might fail to give you what you want.