使用 roxygen2 的 R 包中具有相同的功能但具有两个不同的名称？

Question

I want to create two functions that are exactly the same but have different names in a roxygen2-made R package.

Desired outcome

To be very clear, suppose

first <- function(x) {
  x + 2
}

I would like another function second such that

identical(first, second)
# [1] TRUE

What I know so far

A function can be given an alias , but that doesn't mean its alias is a callable function - rather, it means that you can call ?myalias to display the help file for the original function . But myalias is not a callable function within the package - ie you can't actually use it for anything other than ? .

From Hadley's documentation:

An alias is another name for the topic that can be used with ?.

An inelegant solution

The same function under two different names is possible by brute force - ie by duplicating the file in which the original function is declared and simply changing its name in the duplicate code.

This is obviously tedious, violates DRY , and introduces bloat.

Question

Is there a better way; one that doesn't involve large scale duplication of code?

Answer 1

Use

#' @rdname first
#' @export
second <- first

Your example

So if first.R initially looked like this

#' A function that adds 2
#' @name first
#' @usage first(x)
#' @param x a number
#' @export

first <- function(x) {
  x + 2
}

Then simply include the extra lines of code like so (the last 3 lines are all that change)

#' A function that adds 2
#' @name first
#' @usage first(x)
#' @param x a number
#' @export

first <- function(x) {
  x + 2
}

#' @rdname first
#' @export
second <- first