st: adding variables to a new data file

[David Epstein <david.l.epstein@gmail.com>]

Dear Stata-folks,

This must be a really easy question to answer, but I'm feeling
stumped. I have a data set with a large number of variables in it. I
want to create a new data set with a subset of those variables, with
the exact variables to be exported being read off a loop a few
variables at a time.

So for instance I first want to export the key identifying variable,
which in my case is date. So I will:

preserve
keep date
save temp, replace
restore

Then I'll loop through my loop once and get the names of five
variables I want to add to temp, call them v1 v2 v3 v4 v5. The next
time through, I'll get variables v6 through v10, and so on until I've
added, say 50 variables to temp.

My question is, what do my loops look like? Am I merging each time
through? Keeping, say, date v1 v2 v3 v4 v5, merging, then restoring? I
could, but that seems like it could take a while to keep preserving
and restoring all the time. Plus, I keep having to save the temp file
and then switch back to the master data set. Isn't there a command
that says "take these variables from my current data set and add them
to another data set?"

Any help appreciated.

David Epstein
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