编写 R package 时如何导入“%>%”？

Question

I'm running into the following error when loading an R package I'm writing.

Error in nations %>% rvest::html_nodes(".x") %>% rvest::html_nodes(".y") %>%  : 
  could not find function "%>%"

I'm not sure how to import this in my R package. This is how I have my function setup

 nations_url_odd<-nations %>%
    rvest::html_nodes('.x') %>%
    rvest::html_nodes('.y') %>%
    rvest::html_nodes('a')

Answer 1

Create a reexports.R file in your package with the following lines:

#' @importFrom magrittr %>%
#' @export
magrittr::`%>%`

This will make the pipe available to your package and also reexport it to users of your package, so when they load or attach your package the pipe will be available to them (they won't have to also load magrittr). This can be automated with usethis::use_pipe() (see https://usethis.r-lib.org/reference/use_pipe.html ). As @user2554330 mentions below, this solution depends on the use of roxygen2 .

Answer 2

@Wil gives the best solution if you're a roxygen2 user. If not, then as @ArtemSokolov said in a comment, add this line to your NAMESPACE file:

importFrom(magrittr,"%>%")

If you also want users of your package to be able to use the pipe without a library(magrittr) call or similar, also add this line to NAMESPACE :

export("%>%")

You'll also need to make sure your DESCRIPTION file includes magrittr on the Imports: line, eg

Imports: magrittr