Missing values generated when used command predict

[Seungwoo Kang]

I tried to produce sensitivity and specificity by manually through predict using the result of svy:logit. Below is the syntax I wanted to apply.

svy:logit y x1 x2 ... , nolog or allbaselevels
predict prediction, pr
gen byte predicted = (prediction > 0.1) & !missing(prediction)
svy, subpop(if srh2021 == 1): proportion predicted
svy, subpop(if srh2021 == 0): proportion predicted

However, it shows

predict prediction, pr
(999 missing values generated)

thus, missing portion deterred having an expected result. How to cope with those 999 missing values?

[Jared Greathouse]

I can't work with just syntax, a need a small dataset i can apply this syntax to in order to reproduce the problem.

[Carlo Lazzaro]

Seungwoo:
as an aside to Jared's wise advice, did Stata throw a message about a number of observations ruled out from the estimate due to outcome perfect prediction?