Adding a class "factor"
will ensure that numeric codes are
given integer storage mode. For historical reasons (these names are used when deparsing),
attributes ".Dim"
, ".Dimnames"
, ".Names"
,
".Tsp"
and ".Label"
are renamed to "dim"
,
"dimnames"
, "names"
, "tsp"
and "levels"
.
It is possible to give the same tag more than once, in which case the
last value assigned wins. As with other ways of assigning attributes,
using tag = NULL
removes attribute tag
from .Data
if
it is present.