This article describes how to go from a standard table...
...to a table with an additional row that computes the difference between specified rows:
A table with multiple rows.
1. Select your table.
2. Go to Properties > RULES on the object inspector.
3. To apply the rule, select the Plus (+) > Browse Online Library > Table Computations > Difference Between a Pair of Rows.
4. OPTIONAL: Select the Statistic to use (if different from the default).
5. Select the row under Row 1 to compute the difference from.
6. Select the row under Row 2 to compare against.
7. Press OK.
This rule calculates then the difference between these two rows and displays it beneath the second row. Note, this rule can only apply to a single statistic and no significance tests are conducted on these cells. It is also not compatible with tables that have row spans.
Note, if you select Switch rows and columns on your table, the rule will no longer work due to the table dimensions changing. In this case, you will have to apply the Difference Between a Pair of Columns rule instead.