/PCOMPUTE&postcompute=EXPR(expression)/PPROPERTIES&postcompute… [LABEL=string] [FORMAT=[summary format]…] [HIDESOURCECATS={NO|YES}
Computed categories, also called postcomputes, are
categories created using arithmetic on categories obtained from the
data.  The PCOMPUTE subcommand creates a postcompute, which may
then be used on CATEGORIES within an explicit category list
(see CTABLES Explicit Category List).  Optionally,
PPROPERTIES refines how a postcompute is displayed.  The
following sections provide the details.