Help with foreach loop in Stata 17

[Ksenia Petrova]

Please help to write foreach loop correctly. The following produces an error 'variable var not found'

foreach var of varlist V9 V12 V17 {
replace var = var[.] if var == 9 | var == 8
}

while code like this works

replace V9 = V9[.] if V9 == 9 | V9 == 8
replace V12 = V12[.] if V12 == 9 | V12 == 8
replace V17 = V17[.] if V17 == 9 | V17 == 8

[Jeff Pitblado (StataCorp)]

foreach creates local macro var which needs to be expanded. Also it is unclear what you expect from V9[.], but what you get is a missing value, so better to be explicit. Here is how your loop should be coded

foreach var of varlist V9 V12 V17 {
        replace `var' = . if `var' == 9 | `var' == 8
}

[Nick Cox]

V9[.] works fortuitously in that reference to a value with a missing subscript is treated as a reference to a missing value.

The error in your loop is different.

foreach var of varlist V9 V12 V17 {
    replace `var' = . if `var' == 9 | `var' == 8
}

No loop is needed, as you could use mvdecode instead.

[Ksenia Petrova]

foreach creates local macro var which needs to be expanded. Also it is unclear what you expect from V9[.], but what you get is a missing value, so better to be explicit. Here is how your loop should be coded

foreach var of varlist V9 V12 V17 {
replace `var' = . if `var' == 9 | `var' == 8
}

Thank you so much! [.] was for changing 8 and 9 variable values to missing