SPSS® 12.0 Command Syntax Reference

94 AGGREGATE
Example
AGGREGATE OUTFILE=AGGEMP
/BREAK=LOCATN DEPT (A) TENURE (D)
/AVGSAL = MEAN(SALARY).
• BREAK names the variables LOCATN, DEPT, and TENURE as the break variables.
• Cases in the aggregated file are sorted in ascending order of LOCATN, in ascending order
of DEPT within LOCATN, and in descending order of TENURE within LOCATN and DEPT.
For each group defined by these variables, AVGSAL is computed as the mean of salary.
DOCUMENT Subcommand
DOCUMENT copies documentation from the original file into the aggregated file. By default,
documents are dropped from the aggregated file, whether the file is the working file or an
SPSS-format data file. DOCUMENT must appear after OUTFILE but before BREAK.
PRESORTED Subcommand
PRESORTED indicates that cases in the working data file are sorted according to the values of
the break variables. Without PRESORTED, AGGREGATE must store the entire result data set
in memory. With PRESORTED, it stores only one result case in memory. Thus, specifying
PRESORTED reduces the memory needed and makes AGGREGATE run faster.
• If specified, PRESORTED must precede BREAK. The only specification is the keyword
PRESORTED. PRESORTED has no additional specifications.
• When PRESORTED is specified, the program forms an aggregate case out of each group
of adjacent cases with the same values for the break variables.
• If the working file is not sorted by the break variables in ascending order and PRESORTED
is specified, a warning message is generated but the procedure is executed. Each group of
adjacent cases with the same values for break variables forms a case in the aggregated file,
which may produce multiple cases with the same values for the break variables.
Example
AGGREGATE OUTFILE=AGGEMP
/PRESORTED
/BREAK=LOCATN DEPT
/AVGSAL = MEAN(SALARY).
• PRESORTED indicates that cases are already sorted by the variables LOCATN and DEPT.
• AGGREGATE does not make an extra data pass to sort the cases.
Aggregate Functions
An aggregated variable is created by applying an aggregate function to a variable in the
working file. The variable in the working file is called the source variable, and the new
aggregated variable is the target variable.
• The aggregate functions must be specified last on AGGREGATE.