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 average:

Requirements

Select your table.
Go to Properties > 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 on the table are not changed by this rule. That is, they reflect the results for the original, un-rolled statistics.