oneToNULL: Convert a value of 1 to a NULL value.
Description
oneToNull
is a utility function that returns NULL when a value of
0 or 1 is passed to it, otherwise it returns the original value.
Usage
oneToNULL(value, convertOneToNULL)
Arguments
convertOneToNULL
TRUE to convert 1 to NULL.
Value
NULL if value is 0 or 1, otherwise value.