Aggregate Data

Aggregate Data aggregates groups of cases in the active dataset into single cases and creates a new, aggregated file or creates new variables in the active dataset that contain aggregated data. Cases are aggregated based on the value of zero or more break (grouping) variables. If no break variables are specified, then the entire dataset is a single break group.

If you create a new, aggregated data file, the new data file contains one case for each group defined by the break variables. For example, if there is one break variable with two values, the new data file will contain only two cases. If no break variable is specified, the new data file will contain one case.
If you add aggregate variables to the active dataset, the data file itself is not aggregated. Each case with the same value(s) of the break variable(s) receives the same values for the new aggregate variables. For example, if gender is the only break variable, all males would receive the same value for a new aggregate variable that represents average age. If no break variable is specified, all cases would receive the same value for a new aggregate variable that represents average age.

Break Variable(s). Cases are grouped together based on the values of the break variables. Each unique combination of break variable values defines a group. When creating a new, aggregated data file, all break variables are saved in the new file with their existing names and dictionary information. The break variable, if specified, can be either numeric or string.

Aggregated Variables. Source variables are used with aggregate functions to create new aggregate variables. The aggregate variable name is followed by an optional variable label, the name of the aggregate function, and the source variable name in parentheses.

You can override the default aggregate variable names with new variable names, provide descriptive variable labels, and change the functions used to compute the aggregated data values. You can also create a variable that contains the number of cases in each break group.

To Aggregate a Data File

From the menus choose:
Data > Aggregate...
Optionally select break variables that define how cases are grouped to create aggregated data. If no break variables are specified, then the entire dataset is a single break group.
Select one or more aggregate variables.
Select an aggregate function for each aggregate variable.

Optionally, you can override the default aggregate variable names with new variable names, provide descriptive variable labels, and create a variable that contains the number of cases in each break group.

Saving Aggregated Results

You can add aggregate variables to the active dataset or create a new, aggregated data file.

Add aggregated variables to active dataset. New variables based on aggregate functions are added to the active dataset. The data file itself is not aggregated. Each case with the same values of the break variables receives the same values for the new aggregate variables.
Create a new dataset containing only the aggregated variables. Saves aggregated data to a new dataset in the current session. The dataset includes the break variables that define the aggregated cases and all aggregate variables defined by aggregate functions. The active dataset is unaffected.
Write a new data file containing only the aggregated variables. Saves aggregated data to an external data file. The file includes the break variables that define the aggregated cases and all aggregate variables defined by aggregate functions. The active dataset is unaffected.

Sorting Options for Large Data Files

For very large data files, it may be more efficient to aggregate presorted data.

File is already sorted on break variables. If the data have already been sorted by values of the break variables, this option enables the procedure to run more quickly and use less memory. Use this option with caution.

Data must by sorted by values of the break variables in the same order as the break variables specified for the Aggregate Data procedure.
If you are adding variables to the active dataset, select this option only if the data are sorted by ascending values of the break variables.

Sort file before aggregating. In very rare instances with large data files, you may find it necessary to sort the data file by values of the break variables prior to aggregating. This option is not recommended unless you encounter memory or performance problems.