User Guide

36
Chapter 3
You can also aggregate data after reading it into SPSS, but preaggregating may
save time for large data sources.
E Select one or more break variables that define how cases are grouped to create
aggregated
data.
E Select one
or more aggregate variables.
E Select an a
ggregate function for each aggregate variable.
Optionally, you can create a variable that contains the number of cases in each
break group.
Note:Ifyou
use random sampling, aggregation is not available.
Defining Variables
Variable names and lab els. The complete database field (column) name is used as the
variable l
abel. Unless you modify the variable name, the Database Wizard assigns
variable names to each column from the database in one of two ways:
 If the name of the database field forms a valid, unique variable name, it is used
as the vari
able name.
 If the nam
e of the database field does not form a valid, unique variable name, a
new, unique name is automatically generated.
Click any c
elltoeditthevariablename.
Converting strings to numeric values. Check the Recode to Numeric box for a string
variable if you want to automatically convert it to a numeric variable. String values
are conve
rted to consecutive integer values based on alphabetic order of the original
values. The original values are retained as value labels for the new variables.
Width for variable-width strings. Controls the width of variable-width string values.
By defaul
t, the width is 255 bytes, and only the first 255 bytes (typically 255
characters in single-byte languages) will be read. The width can be up to 32,767
bytes. Although you probably don’t want to truncate string values, you also don’t
want to s
pecify an unnecessarily large value, since excessively large values will
cause SPSS processing to be inefficient.