st: gen & summation

["Ziad El-Khatib" <Ziad.El-Khatib@ki.se>]

Hi
very strange result is happening when i try to


gen total=day1+day2+day3 if select==1


STATA gives
(1330 missing values generated)

Although the above variables (day1,2,3) contain numeric values, any tips?


Thank you and best regards
ziad
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