User Guide

167
Data Transform
ations

Create new time series variables as functions of existing time series variables.
 Replace system- and user-missing values with estimates based on one of several
methods.
A time series is obtained by measuring a variable (or set of variables) regularly over a
period of time. Time series data transformations assume a data file structure in
which each c
ase (row) represents a set of observations at a different time, and the
length of time between cases is uniform.
Define Dat
es
The Define
Dates dialog box allows you to generate date variables that can be used to
establish the periodicity of a time series and to label output from time series analysis.
Figure 7-3
0
Define Dat
es dialog box
Cases Are. Defines the time interval used to generate dates.
 Not dated removes any previously defined date variables. Any variables with the
following names are deleted: year_, quarter_, month_, week_, day_, hour_,
minute_, second_,anddate_.
 Custom indicates the presence of custom date variables created with command
syntax (for example, a four-day work week). This item merely reflects the current
state of the working data file. Selecting it from the list has no effect. (See the