If no other arguments are supplied it depends on the type of x. The last item
of a vector or list. The last row of a data.frame
or data.table
.
Otherwise, whatever xts::last
returns (if package xts has been loaded,
otherwise a helpful error).
If any argument is supplied in addition to x
(such as n
or
keep
in xts::last
), regardless of x
's type, then
xts::last
is called if xts has been loaded, otherwise a helpful error.