Brian S. Everitt A Handbook of Statistical Analyses using SPSS

Display 1.11 Selecting subsets of cases for later analyses.
in the Data View spreadsheet and ignores these rows in subsequent analyses.
It also automatically includes a filter variable, labeled filter_$ in the
spreadsheet which takes the value “1” for selected rows and “0” for
unselected rows. Filter variables are kept to enable replication of the case
selection at a later stage by simply selecting cases for which filter_$ takes
the value “1.” Once the selection is active, the status bar displays “Filter
On” for information. (It is also possible to remove unselected cases
permanently by checking Unselected Cases Are Deleted in the Select Cases
dialogue box, Display 1.11.)
1.5.2 Generating New Variables
The Transform drop-down menu provides procedures for generating new
variables or changing the values of existing ones (Display 1.12).
The Compute… command is frequently used to generate variables suitable
for statistical analyses or the creation of graphics. The resulting
Compute dialogue can be used to create new variables or replace the values
of existing ones (Display 1.13). The name of the variable to be created
or for which values are to be changed is typed in the Target Variable list.
For new variables, the Type&Label sub-dialogue box enables specification
of variable type and label. The expression used to generate new values
can be typed directly in the Expression field or constructed automatically
by pasting in functions from the Functions list or selecting arithmetic
operators and numbers from the “calculator list” seen in Display 1.13.
When pasting in functions, the arguments indicated by question marks
must be completed. Here, for example, we request a new variable, the
age of a person in months (variable month), to be generated by multiplying
the existing age variable in years (age) by the factor 12 (Display 1.13).
© 2004 by Chapman & Hall/CRC Press LLC