r pass name of list as string in custom function

Question

I need to pass the name of a list as a string to a mutate column as part of a custom function. For e.g.:

a_list = c('a','b','c')

test = function(list_name) {
  map_df(list_name, function(x) {
    benchmark(x = paste(x,'test')) %>% 
      mutate(test = x,
             list_name_as_string = deparse(substitute(list_name)))
  })
}

test(a_list)

gives:

  test replications elapsed relative user.self sys.self user.child sys.child list_name_as_string
1    a          100       0       NA         0        0         NA        NA           list_name
2    b          100       0       NA         0        0         NA        NA           list_name
3    c          100       0       NA         0        0         NA        NA           list_name

I want the last column to be "a_list" repeated.

THanks

You call a_list a list, but it is a vector, not a list(). Being careful with that terminology can help avoid headaches later. — Gregor Thomas
– Gregor Thomas, Commented May 20, 2021 at 18:52
Yes thanks. In my real world problem it is a list; I should have been more clear here. — jkud
– jkud, Commented May 21, 2021 at 20:19

LMc · Accepted Answer · 2021-05-20 18:35:43Z

Try the evaluation before the assignment:

a_list = c('a','b','c')

test <- function(list_name) {
  j <- deparse(substitute(list_name))
  
  map_df(list_name, ~ benchmark(x = paste(.x, 'test')) %>%
           mutate(test = .x,
                  list_name_as_string = j))
}

test(a_list)

Or use map2_df:

test <- function(list_name){
  map2_df(list_name, deparse(substitute(list_name)), ~
            benchmark(x = paste(.x,'test')) %>%
            mutate(test = .x,
                   list_name_as_string = .y)
  )
}

Output

  test replications elapsed relative user.self sys.self user.child sys.child
1    a          100       0       NA         0        0         NA        NA
2    b          100       0       NA         0        0         NA        NA
3    c          100       0       NA         0        0         NA        NA
  list_name_as_string
1              a_list
2              a_list
3              a_list

akrun · Accepted Answer · 2021-05-20 18:55:16Z

1

As we are using tidyverse, we can also use the syntax

test <- function(list_name) {
  str1 <- rlang::expr_text(rlang::enexpr(list_name))
 purrr::map_df(list_name, function(x) {
   rbenchmark::benchmark(x = paste(x,'test')) %>% 
     dplyr::mutate(test = x,
            list_name_as_string = str1)
 })
  
}

-testing

test(a_list)
#    test replications elapsed relative user.self sys.self user.child sys.child list_name_as_string
#1    a          100   0.001        1     0.001        0          0         0              a_list
#2    b          100   0.001        1     0.001        0          0         0              a_list
#3    c          100   0.001        1     0.001        0          0         0              a_list

answered May 20, 2021 at 18:55

akrun

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