st: sum up many variables with missing values across columns

[Daifeng He <dhe.statlist@gmail.com>]

Hi there,

I am trying to sum up say 100 variables across columns, but many of
the 100 variables have missing values. And I want the sum to be
missing if any of the 100 variables is missing.   -rowtotal- does not
work because it treats missing values as 0; even with the option -,
missing-, it generates a missing value only when all the 100 variables
are missing.

Does anybody know how to do this efficiently instead of typing varx+
vary+ var z+... varxx+varyy+varzz?  My variables do not have a common
stub in the variable names so I cannot use a loop.

Thanks for the help.

Daifeng
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