xtfrm: Auxiliary Function for Sorting and Ranking
Description
A generic auxiliary function that produces a numeric vector which
will sort in the same order as x.Value
A numeric (usually integer) vector of the same length as x.Details
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. The factor method extracts the codes. The
Surv method sorts first on times and then on
status code(s), finally on timme2 if present. Note that with
the conventional status codes this sorts individuals still alive before
deaths. The default method will unclass the object if
is.numeric(x) is true but otherwise make use of
== and > methods for the class of x[i] (for
integers i), and the is.na method for the class of
x, but might be rather slow when doing so. This is an internal generic primitive, so S3 or S4
methods can be written for it.