Insert missing cases (within id)

** Job is to ensure that all id have the 4 quarters present.
** rlevesque@videotron.ca.

data list free / id quarter wages.
begin data
1 1 6000 
1 3 6100 
2 1 7000 
2 2 7200
2 4 7150
end data .

*Your data file must be sorted.
SORT CASES BY id quarter.
SAVE OUTFILE='c:\\temp\\data temp.sav'.

AGGREGATE
  /OUTFILE=*
  /BREAK=id
  /quarter = N(quarter).

* Create a file with each id and all 4 quarters.
LOOP qtr=1 TO 4.
+ XSAVE OUTFILE='temp.sav' /KEEP=id qtr.
END LOOP.
EXECUTE.
GET FILE='temp.sav'.
RENAME VARIABLE (qtr=quarter).

* Matching the 2 files fills in the gaps.
MATCH FILES /FILE=*
 /FILE='C:\\temp\\data temp.sav'
 /BY id quarter.
EXECUTE.