Differences between revisions 2 and 8 (spanning 6 versions)
⇤ ← Revision 2 as of 2021-10-01 15:06:09 →
Size: 917
Editor: DominicRicottone
Comment:
← Revision 8 as of 2023-06-12 15:43:48 → ⇥
Size: 1971
Editor: DominicRicottone
Comment:
Deletions are marked like this. Additions are marked like this.
Line 3: Line 3:
SPSS offers a couple options for looping, but overall is less flexible as compared to other languages. SPSS offers a couple options for '''looping''', but overall is less flexible as compared to other languages.
Line 11: Line 11:
== DO REPEAT == == Arbitrary Lists ==
Line 13: Line 13:
One method of looping that is '''only valid for data transformation commands''' (i.e. `COMPUTE`) is the `DO REPEAT ... END REPEAT` command.

As demonstrated below, `DO REPEAT` can iterate over...
 * arbitrary sequences
 * variable ranges (either existing or new)
 * integer ranges

Multiple sequences/ranges can be iterated over in parallel as long as each has the same number of elements.		 The [[SPSS/DoRepeat|DO REPEAT]] command can loop over arbitrary, fixed-length lists.
Line 23: Line 16:
do repeat X=A B C D E / Y=new1 to new5 / Z=1 to 5.
  if (original=Z) Y=ltrim(rtrim(X)).		 do repeat X='A' 'B' 'C' 'D' 'E'.
  if ltrim(rtrim(foo))=X bar=1.
Line 28: Line 21:
To print the evaluated loop syntax, use `END REPEAT PRINT`. ----



== Integer Ranges ==

The [[SPSS/DoRepeat|DO REPEAT]] command can loop over an integer range.

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

The [[SPSS/Loop|LOOP]] command can be used similarly.

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

----



== Variable Lists ==

The [[SPSS/DoRepeat|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 [[SPSS/Loop|LOOP]] command with a [[SPSS/Vectors|vector]].

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

----



== Conditional Looping ==

The [[SPSS/Loop|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 [[SPSS/Loop|LOOP]] command can also be made loop indefinitely, if no `IF` option is specified.

{{{
loop.
  compute foo = replace(foo,' ',' ').
end loop.
}}}
Line 36: Line 104:
Advanced looping can be handled through macro programming. See [[SPSS/Macros#Loops]] for examples. Advanced looping can be handled through macro programming. See [[SPSS/Macro/Looping|here]] for examples.

SPSS Looping

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

Contents

  1. SPSS Looping
    1. Arbitrary Lists
    2. Integer Ranges
    3. Variable Lists
    4. Conditional Looping
    5. Indefinite Looping
    6. Macros

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.

CategoryRicottone

SPSS/Looping (last edited 2023-06-12 15:43:48 by DominicRicottone)