st: _byn1() and _byn2() variables in numlist

["Poliquin, Christopher" <cpoliquin@hbs.edu>]

Hello,

I am attempting to use the _by variables in a byable program, but am running into problems with syntax problems and invalid numlists that I cannot figure out how to resolve:

I do...

. program testing, byable(recall)
  1.         marksample touse
  2.         di _byn2()
  3.         di _byn1()
  4.         forvalues x = _byn2()(-1)_byn1() {
  5.                 di `x'
  6.         }
  7. end
. bys foo : testing


And get ...
----------------------
-> foo = 1
2
1
invalid syntax
r(198);

And when using a numlist, i.e. foreach x of numlist _byn2()(-1)_byn1(), I get an invalid numlist error.

How do I cycle through each observation number in a group within a byable program?

Best wishes,
Chris

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