codes(object)
object is not ordered)
of
object for the corresponding element of
object.
object does not inherit from
"factor", then
as.vector(object)
is returned.
In the case of an ordered factor, the result has
1 wherever
the first level occurs,
2 wherever the second occurs, etc.
Thus the ordering relation of the levels is preserved.
In the case of an unordered factor, the levels are sorted
and
1 appears wherever the first of the ordered levels occurs,
etc.
This maintains the definition of the levels of a factor as a set;
that is, the behavior of the factor is independent of the order
in which the levels appear in the levels attribute.
Users should not strip the class from a factor and expect correct results.
codes(ordered(c("cat", "dog", "frog", "dog")))
# returns c(1, 2, 3, 2)
temperature <- ordered(c(140, 140, 125, 125, 130, 130))
as.vector(temperature, "numeric")
# coerce to numeric, returns c(140, 140, 125, 125, 130, 130)