st: generate sum of variables & ignore missing

[Andrea Bennett <mac.stata@gmail.com>]

Hi,

I guess this is an easy task for somebody more experienced. I have 3  
columns (varA, varB, varC) containing dummy variables (0, 1, missing  
values "."). I would like to generate "varD" the sum of each row, e.g.  
if varA==1 varB==0 varC==1 I should have varD==2. This works clearly  
fine when there are no missing values (varD= varA + varB + varC). But  
is there an easy way to let Stata read a missing value as "0" so that  
varA==1 varB==. varC==1 would result in varD==2 (without actually  
replacing the missing values with "0")? I am trying to get it to work  
with -missing()- but so far have not succeeded.

Many thanks for your consideration,

Andrea
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