SPSS Looping

SPSS offers a couple options for looping, but overall is less flexible as compared to other languages.

Arbitrary Lists

The DO REPEAT command can loop over arbitrary, fixed-length lists.

do repeat X='A' 'B' 'C' 'D' 'E'.
  if ltrim(rtrim(foo))=X bar=1.
end repeat.

Integer Ranges

The DO REPEAT command can loop over an integer range.

do repeat Y=1 to 5.
  if foo=X bar=1.
end repeat.

The LOOP command can be used similarly.

loop #y=1 to 5 by 1.
  if foo=#y bar=1.
end loop.

Variable Lists

The DO REPEAT command can loop over variables. If the variables are not pre-existing, a range is extrapolated from the variable names.

do repeat Z=new1 to new5.
  compute Z=foo.
end repeat.

A similar effect can be acheived by using the LOOP command with a vector.

vector new(4).
loop #z = 1 to 4.
  compute new(#z) = (foo=#z).
end loop.

Conditional Looping

The LOOP command can loop a variable number of times, based on either a 'while' or a 'break' condition. Specify the IF option on the LOOP command for the former behaviuor, or on the END LOOP command for the latter.

loop.
  compute foo = replace(foo,'  ',' ').
end loop if char.index(foo,'  ') = 0.

loop if char.index(foo,'  ') > 0.
  compute foo = replace(foo,'  ',' ').
end loop.

Indefinite Looping

The LOOP command can also be made loop indefinitely, if no IF option is specified.

loop.
  compute foo = replace(foo,'  ',' ').
end loop.

Macros

Advanced looping can be handled through macro programming. See here for examples.

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