NULLCPO is the neutral element of CPO and CPOTrained composition when using %>>% or composeCPO. It is furthermore no effect when attached to a Learner using attachCPO (or %>>%), or when applied to data using applyCPO, invert, or predict (or, again, %>>%).

NULLCPO works as a stand-in for certain operations that have an "empty" return value: It is returned when retrafo and inverter are applied to an object that has no retrafo or inverter associated with it, and by pipeCPO when applied to an empty list.

NULLCPO can be checked using is.nullcpo, and converted from or to NULL using nullToNullcpo and nullcpoToNull. Otherwise it behaves very similarly to other CPO or CPOTrained objects.



An object of class NULLCPO (inherits from CPOPrimitive, CPORetrafo, CPOInverter, CPOTrained, CPO) of length 0.

See also