dplyr arrange() works with single variable inside c(), but not multiple variables inside of c() when evaluated inside of a function

Question

Everything I can find online about tidyeval is either older and not up to date with latest version of tidyverse\dplyr or else doesn't quite apply.

An example tibble is:

df <- tribble(
       ~var1, ~var2, ~var3,
         1,     2,     3,
         4,     5,     6,
         7,     8,     9
        )

I have a small function that I've written:

fun <- function(data, select_var, arrange_var) {
   select_var <- enquo(select_var)
   arrange_var <- enquo(arrange_var)

   data %>%
     select(!!select_var) %>%
     arrange(!!arrange_var)
   }

The function simply selects column(s) and then arranges by row(s).

When I pass the arguments to the function it works fine with a single variable inside of c():

fun(df, 
    c(var1,
      var2)),
    c(var2))

However, when I try to pass it two variables like this:

    fun(df, 
    c(var1,
      var2)),
    c(var1,
      var2))

I get the following error:

Error: incorrect size (282) at position 1, expecting : 141

The closest stack responses I've been able to find are: arrange() doesn't recognize column name parameter and Pass a vector of variable names to arrange() in dplyr

but both of these seem to give answers that included deprecated solutions (e.g., arrange_())

Some great information here: tidyeval resource roundup by Mara Averick

and Separating and Trimming Messy Data the Tidy Way by Paul Oldham

and of course I've dug into: tidyeval

However none of them seem to address this quirk. I've exhausted my resources after spending an afternoon. The code works find in a standard R file, just can't get it to work inside of a function, but about ready to give up, so thought I would see if you wonderful folks could help. Thanks in advance.

Answer 1

Update 2022/03/17

The tidyverse has evolved and so should this answer.

There is no need for enquo anymore! Instead we enclose tidy-select expressions in double braces {{ }}.

library("tidyverse")

df <- tribble(
  ~var1, ~var2, ~var3,
  1, 2, 3,
  4, 5, 6,
  7, 8, 9
)

fun <- function(data, select_vars, ...) {
  data %>%
    select(
      {{ select_vars }}
    ) %>%
    arrange(
      ...
    )
}


fun(df, c(var1, var2), desc(var2))
#> # A tibble: 3 × 2
#>    var1  var2
#>   <dbl> <dbl>
#> 1     7     8
#> 2     4     5
#> 3     1     2
fun(df, c(var1, var2), var1, var2)
#> # A tibble: 3 × 2
#>    var1  var2
#>   <dbl> <dbl>
#> 1     1     2
#> 2     4     5
#> 3     7     8

We still can't use c() with the arrange and filter verbs because that's not allowed with data-masking.

df %>%
  arrange(
    c(var1, var2)
  )
#> Error in `arrange()`:
#> ! Problem with the implicit `transmute()` step.
#> x Problem while computing `..1 = c(var1, var2)`.
#> x `..1` must be size 3 or 1, not 6.

^{Created on 2022-03-17 by the reprex package (v2.0.1)}

Old answer

Replacing arrange_var with ... and specifying the variables without enclosing them in c() makes it work.

library("dplyr")

df <- tribble(
  ~var1, ~var2, ~var3,
  1, 2, 3,
  4, 5, 6,
  7, 8, 9
)

fun <- function(data, select_var, ...) {
  select_var <- enquo(select_var)
  data %>%
    select(!!select_var) %>%
    # You can pass the dots to `arrange` directly
    arrange(...)
}

fun(df, c(var1, var2), var2)
#> # A tibble: 3 x 2
#>    var1  var2
#>   <dbl> <dbl>
#> 1     1     2
#> 2     4     5
#> 3     7     8
fun(df, c(var1, var2), var1, var2)
#> # A tibble: 3 x 2
#>    var1  var2
#>   <dbl> <dbl>
#> 1     1     2
#> 2     4     5
#> 3     7     8

^{Created on 2019-03-08 by the reprex package (v0.2.1)}

It turns out that only select supports strings and character vectors. As the documentation says, "This is unlike other verbs where strings would be ambiguous." See the last example for dplyr::select.

# Two alternatives; both work with `select`.
df %>%
  select(var1, var2)
#> # A tibble: 3 x 2
#>    var1  var2
#>   <dbl> <dbl>
#> 1     1     2
#> 2     4     5
#> 3     7     8
df %>%
  select(c(var1, var2))
#> # A tibble: 3 x 2
#>    var1  var2
#>   <dbl> <dbl>
#> 1     1     2
#> 2     4     5
#> 3     7     8

# `arrange` only works with lists on comma separated unquoted variable names.
df %>%
  arrange(var1, var2)
#> # A tibble: 3 x 3
#>    var1  var2  var3
#>   <dbl> <dbl> <dbl>
#> 1     1     2     3
#> 2     4     5     6
#> 3     7     8     9
df %>%
  arrange(c(var, var2))
#> Error: incorrect size (4) at position 1, expecting : 3

^{Created on 2019-03-08 by the reprex package (v0.2.1)}