%in%.
x %nin% y
x %kin% y
x %knin% yNULL: the values to be
matched.NULL: the values to be matched
against.%nin% returns a logical vector indicating if there
is no match for its left operand. It is the inverse of
x %in% y.%kin% returns the actual values of x for
which x %in% y.
%knin% returns the actual values of x for
which x %nin% y.