A generic auxiliary function that produces a numeric vector which
will sort in the same order as
an R object.
A numeric (usually integer) vector of the same length as
This is a special case of ranking, but as a less general function than
rank is more suitable to be made generic. The default
method is similar to
rank(x, ties.method = "min",
na.last = "keep"), so
NA values are given rank
NA and all
tied values are given equal integer rank.
factor method extracts the codes.
The default method will unclass the object if
is.numeric(x) is true but otherwise make use of
> methods for the class of
i), and the
is.na method for the class of
x, but might be rather slow when doing so.