Missing Values & the Generation of New Variables

[Jia De Gedeon Lim]

Hey everyone,

I noticed that my Stata gives me a missing value when I generate a new variable that equals the sum of two other variables when the value of either one variable is missing.

E.g. from Ajay's solowhh_dataprep.do

arisredsload hh82/Deck 9.dta

gen vfarmasst = v9 + v10

collapse (sum) vfarmasst, by(v3)
rename v3 id1982
sort id1982
tempfile farmasst82
save `farmasst82'

Running the first part of the code (gen vfarmasst...) actually generates 6014 missing values but in some of these cases, for e.g., v9 is missing but v10 has a integer value. It is just the case that Stata, probably treating . as a infinite value (?) codes vfarmasst with a missing value as well.

Just thought I'd point this out 'cos I never realized that my Stata does this and I'm wondering if it's a problem that occurs only on a/my Macbook or it is a universal occurrence. Thanks!

Best,
Gedeon

[Ajay Shenoy]

This is the issue Raj mentioned where it's better to use egen = rowtotal(), which will treat missing values as zeros (as long as at least one value in the varlist is not missing).  Which is what I should've done here...

-@

[Jia De Gedeon Lim]

Oh i see. Thanks for the clarification Ajay!