How to Create a Rolling Average on Tables

This article describes how to go from a crosstab with a Date/Time variable set...

...to a table with a lagged rolling (aka smoothing or moving) average:

Requirements

Select your table.
Go to Data > Rules in the object inspector.
To apply the rule, select the Plus (+) > Modify Whole Table or Plot > Replace with Rolling Averages.
Set the Number of periods to roll.
OPTIONAL: Tick Dates are in the rows if applicable.
Press OK.

Please note the following:

A lagged rolling average is computed. For example, if January has a score of 3, February 4, and March 6, the 3-period rolling average for March is (3 + 4 + 6) / 3 = 4.33333333.
Where values cannot be computed due to insufficient data, the value is shown as NaN. For example, if January has a score of 3, February 4, and March 6, the 3-period rolling average for the three months, respectively, are NaN, NaN, and 4.33333333.
This rule is only applied to the first statistic selected in each of Statistics > Cells and whichever is appropriate of Statistics > Below and Statistics > Right.
You may not have a NET in the variable containing the dates.
The statistical testing results in the table are not changed by this rule. That is, they reflect the results for the original, unrolled statistics.