st: Loop with capture

[Daniel Escher <descher@nd.edu>]

Hello,

I am looking for advice about how to get my loop to capture and skip a
year, not a variable.

foreach v of newlist x1 x2 x3... {
      capture noisily: {
         capture confirm number `=`i'[1]' // in case that variable
(e.g., unemp1972) already exists
         if _rc==0 {
            cap gen `v'1972 = (`v'1980-`v'1970)/10*2+`v'1970
            cap gen `v'1976 = (`v'1980-`v'1970)/10*6+`v'1970
            cap gen `v'1984 = (`v'1990-`v'1980)/10*4+`v'1980
            ...
            }
      }
}

The problem is that x1 does not exist in 1970, but it does in 1980 and
1990. The loop as written skips the variable x1 instead of just
skipping x11972 and x11976. Can I get the loop to skip just the
year(s) when a variable does not exist?

After reading Nick Cox's article
(http://www.stata-journal.com/sjpdf.html?articlenum=pr0005 (p. 211)),
I realized I could do the following:

foreach v of newlist x1 x2 x3... {
            cap gen `v'1972 = (`v'1980-`v'1970)/10*2+`v'1970
            cap gen `v'1976 = (`v'1980-`v'1970)/10*6+`v'1970
...
}

That's a good work-around for now, but in the future, is there a way
to avoid putting "cap" at the start of each command line? Thank you
for your help.


Gratefully,
Daniel
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