Vectorizing a tidyverse function with `...`

user_16762740 0
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Function foo below recodes the numeric column var1 into a string column (1 --> "a", 2 --> "b" etc.).

I was wondering how to vectorize this function such that instead of argument var1 we have argument ...?

That is, all variables provided in ... should undergo what var1 undergoes in foo.

A possible useful post might be HERE.

library(tidyverse)

foo <- function(data, var1, caps = FALSE, reverse = FALSE){
  
let <-  if(caps) base::LETTERS else base::letters
FUN <- if(reverse) utils::tail else utils::head

data %>% mutate(var1 = factor(FUN(let, max(var1))[var1]))  
}

# EXAMPLE OF USE:
(dat <- data.frame(var1 = c(2,1,3,1,4:1), id = 1:8))

foo(dat, var1, caps = T, reverse = T)
rlang tidyverse vectorization r function
2 Answers

We may use across -

foo <- function(data, caps = FALSE, reverse = FALSE, ...){
  vars <- rlang::ensyms(...) 
  let <-  if(caps) base::LETTERS else base::letters
  FUN <- if(reverse) utils::tail else utils::head
  
  data %>% mutate(across(as.character(vars), ~factor(FUN(let, max(.))[.])))  
}

dat <- data.frame(var1 = c(2,1,3,1,4:1), id = 1:8)
foo(dat, caps = T, reverse = T, var1)

#  var1 id
#1    X  1
#2    W  2
#3    Y  3
#4    W  4
#5    Z  5
#6    Y  6
#7    X  7
#8    W  8

foo(dat, caps = T, reverse = T, var1, id)

#  var1 id
#1    X  S
#2    W  T
#3    Y  U
#4    W  V
#5    Z  W
#6    Y  X
#7    X  Y
#8    W  Z
user_39629140

The approach below should do what you are looking for. It is not as clean as my answer to the linked post in your question, but it should work as expected (now also updated with default arguments that apply to all variables):

library(tidyverse)
library(rlang)

foo <- function(data, ..., caps = FALSE, reverse = FALSE){
  
  var_ls <- map(ensyms(..., .named = TRUE), as.character)
  l_varls <- length(var_ls) 
  
  if(l_varls != length(caps)) {
    caps <- rep(caps, l_varls)
  }
  if(l_varls != length(reverse)) {
    reverse <- rep(reverse, l_varls)
  }
  
  let <- ifelse(caps, list(base::LETTERS), list(base::letters))
  names(let) <- names(var_ls)
  FUN <- ifelse(reverse, list(utils::tail), list(utils::head))
  names(FUN) <- names(var_ls)
  
  mutate(data,
         purrr::map_dfc(var_ls,
                        ~ factor(FUN[[.x]](let[[.x]],max(data[[.x]]))[data[[.x]]]))
         )
  
}

# EXAMPLE OF USE:
(dat <- data.frame(var1 = c(2,1,3,1,4:1), var2 = c(8:1), id = 1:8))
#>   var1 var2 id
#> 1    2    8  1
#> 2    1    7  2
#> 3    3    6  3
#> 4    1    5  4
#> 5    4    4  5
#> 6    3    3  6
#> 7    2    2  7
#> 8    1    1  8

foo(dat, var1, var2, caps = c(TRUE,FALSE), reverse = c(FALSE, TRUE))
#>   var1 var2 id
#> 1    B    z  1
#> 2    A    y  2
#> 3    C    x  3
#> 4    A    w  4
#> 5    D    v  5
#> 6    C    u  6
#> 7    B    t  7
#> 8    A    s  8
foo(dat, var1, var2)
#>   var1 var2 id
#> 1    b    h  1
#> 2    a    g  2
#> 3    c    f  3
#> 4    a    e  4
#> 5    d    d  5
#> 6    c    c  6
#> 7    b    b  7
#> 8    a    a  8
foo(dat, var1, var2, caps = TRUE, reverse = TRUE)
#>   var1 var2 id
#> 1    X    Z  1
#> 2    W    Y  2
#> 3    Y    X  3
#> 4    W    W  4
#> 5    Z    V  5
#> 6    Y    U  6
#> 7    X    T  7
#> 8    W    S  8

Created on 2021-09-18 by the reprex package (v0.3.0)

user_93493020
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