Loop to drop specific observations

[Julius Doyle]

I'm trying to create a loop that automatically replaces all observations with a "." with exception to the observations associated with a specific Location.

I need some help understanding the anatomy of the syntax because the one I'm trying is not working.

I'm trying:

foreach v in `r(varlist)' {replace `v' = . if Location !== 19}

I'm copying this command from a previous destring loop that I was briefly taught about, so there could be some naiive misunderstanding that's making it non-functional.

I understand that

foreach

refers to literally "for each"

However, the letter v, is confusing. Does stata understand "v" to mean "variable"?

Also, for

`r(varlist)'

, my understanding is that the compound quotations are for strings. Are they necessary here?

What would the correct code be?

Thanks

[Julius Doyle]

I've now worked out the following:

foreach i of local varlist _all {
replace `i' = . if Location !==19
}

Stata then returns an error that says:

{ required

[Nick Cox]

This question is nothing to do with Mata. That sounds picky, I guess, but you would have got a much quicker reply posting in General.

 
 foreach i of local varlist _all {

would be better as

foreach i of var _all {

!= not !== is the not equals operator. That is certainly one reason why the code in #1 would not work.

There are various tutorials on loops here and there. One that is familiar to me is https://journals.sagepub.com/doi/pdf...36867X20976340