xtfrm {base} | R Documentation

## 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`.

### Usage

    xtfrm(x)

### Arguments

`x` | an R object.

### 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).

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.

### Value

A numeric (usually integer) vector of the same length as `x`.

### See Also

`rank`, `sort`, `order`.

[Package base version 2.15.1 Index]