Return object vector (e.g. list of variables) as character vector in R-CodePudding

I would like to return an object vector (e.g. a list of variables) as a character vector in R. This is as close as I've gotten:

library(tidyverse)

data <- as_tibble(mtcars)

foo <- function (vars) {
  as.character(enexpr(vars))
}

foo(c(hp, drat, wt))

I would like this to return [1] "hp" "drat" "wt" but instead I'm getting [1] "c" "hp" "drat" "wt".

The code below works but it seems inelegant (and requires reading in the data):

foo <- function (vars) {
  names(select(data, {{ vars }}))
}

foo(c(hp, drat, wt))

The application is passing a selection of variables to a paste function so that they can be combined to make a formula.

Edit: It goes without saying, this would also obviously work:

foo <- function (vars) {
  as.character(enexpr(vars))[-1]
}

foo(c(hp, drat, wt))

My feeling though is that there still must be a tidier (pun intended) way of doing this.

CodePudding user response：

How about something like this:

library(rlang)
foo <- function(...){
  l <- quos(...)
  sapply(l, quo_name)
}

foo(hp, drat, wt)
#>                      
#>   "hp" "drat"   "wt"

^{Created on 2022-07-06 by the reprex package (v2.0.1)}

CodePudding user response：

I recommend tidyselect for this sort of things.

foo <- function (data, vars) {
  tidyselect::eval_select(enquo(vars), data)
}

foo(mtcars, c(hp, drat, wt))
#>   hp drat   wt
#>    4    5    6

As a bonus you gain all of the tidyselect features:

foo(mtcars, starts_with("d"))
#> disp drat
#>    3    5

Note that you have to supply a data frame. This follows the tidyverse principle that unquoted object names can only refer to existing objects.