User Guide

172
Chapter 7

If you create new series that contain forecasts beyond the end of the existing
series (by c
licking a
Save button and making suitable choices), the original series
and the generated residual series will have missing data for the new observations.
 Some transformations (for example, the log transformation) produce missing data
for certain values of the original series.
Missing data at the beginning or end of a series pose no particular problem; they
simply shor
ten the useful length of the series. Gaps in the middle of a series
(embedded missing data) can be a much more serious problem. The extent of the
problem depends on the analytical procedure you are using.
The Replac
e Missing Values dialog box allows you to create new time series
variables from existing ones, replacing missing values with estimates computed with
one of several methods. Default new variable names are the first six characters of the
existing v
ariable used to create it, followed by an underscore and a sequential number.
For example, for the variable price, the new variable name would be price_1.The
new variables retain any defined value labels from the original variables.
Figure 7-32
Replace Missing Values dialog box