dplyr - programming dynamic variable & function name - ascending & descending - r

Question

I am trying to find way to shorten my code using dynamic naming variables & functions related with ascending & descending order. Though I can do desc but couldn't find anything for ascending. Below is the reproducible example to demonstrate my problem.
Here is the sample dataset
library(dplyr)
set.seed(100)
data <- tibble(a = runif(20, min = 0, max = 100),
b = runif(20, min = 0, max = 100),
c = runif(20, min = 0, max = 100))
Dynamically passing variable with percent rank in ascending order
current_var <- "a" # dynamic variable name
data %>%
mutate("percent_rank_{current_var}" := percent_rank(!!sym(current_var)))
#> # A tibble: 20 × 4
#> a b c percent_rank_a
#> <dbl> <dbl> <dbl> <dbl>
#> 1 30.8 53.6 33.1 0.263
#> 2 25.8 71.1 86.5 0.158
#> 3 55.2 53.8 77.8 0.684
#> 4 5.64 74.9 82.7 0
#> 5 46.9 42.0 60.3 0.526
#> 6 48.4 17.1 49.1 0.579
#> 7 81.2 77.0 78.0 0.947
#> 8 37.0 88.2 88.4 0.421
#> 9 54.7 54.9 20.8 0.632
#> 10 17.0 27.8 30.7 0.0526
#> 11 62.5 48.8 33.1 0.737
#> 12 88.2 92.9 19.9 1
#> 13 28.0 34.9 23.6 0.211
#> 14 39.8 95.4 27.5 0.474
#> 15 76.3 69.5 59.1 0.895
#> 16 66.9 88.9 25.3 0.789
#> 17 20.5 18.0 12.3 0.105
#> 18 35.8 62.9 23.0 0.316
#> 19 35.9 99.0 59.8 0.368
#> 20 69.0 13.0 21.1 0.842
Dynamically passing variable with percent rank in descending order
data %>%
mutate("percent_rank_{current_var}" := percent_rank(desc(!!sym(current_var))))
#> # A tibble: 20 × 4
#> a b c percent_rank_a
#> <dbl> <dbl> <dbl> <dbl>
#> 1 30.8 53.6 33.1 0.737
#> 2 25.8 71.1 86.5 0.842
#> 3 55.2 53.8 77.8 0.316
#> 4 5.64 74.9 82.7 1
#> 5 46.9 42.0 60.3 0.474
#> 6 48.4 17.1 49.1 0.421
#> 7 81.2 77.0 78.0 0.0526
#> 8 37.0 88.2 88.4 0.579
#> 9 54.7 54.9 20.8 0.368
#> 10 17.0 27.8 30.7 0.947
#> 11 62.5 48.8 33.1 0.263
#> 12 88.2 92.9 19.9 0
#> 13 28.0 34.9 23.6 0.789
#> 14 39.8 95.4 27.5 0.526
#> 15 76.3 69.5 59.1 0.105
#> 16 66.9 88.9 25.3 0.211
#> 17 20.5 18.0 12.3 0.895
#> 18 35.8 62.9 23.0 0.684
#> 19 35.9 99.0 59.8 0.632
#> 20 69.0 13.0 21.1 0.158
How to combine both into one statement? - I can do for desc but couldn't find any explicit statement for ascending order
rank_function <- desc # dynamic function for ranking
data %>%
mutate("percent_rank_{current_var}" := percent_rank(rank_function(!!sym(current_var))))
#> # A tibble: 20 × 4
#> a b c percent_rank_a
#> <dbl> <dbl> <dbl> <dbl>
#> 1 30.8 53.6 33.1 0.737
#> 2 25.8 71.1 86.5 0.842
#> 3 55.2 53.8 77.8 0.316
#> 4 5.64 74.9 82.7 1
#> 5 46.9 42.0 60.3 0.474
#> 6 48.4 17.1 49.1 0.421
#> 7 81.2 77.0 78.0 0.0526
#> 8 37.0 88.2 88.4 0.579
#> 9 54.7 54.9 20.8 0.368
#> 10 17.0 27.8 30.7 0.947
#> 11 62.5 48.8 33.1 0.263
#> 12 88.2 92.9 19.9 0
#> 13 28.0 34.9 23.6 0.789
#> 14 39.8 95.4 27.5 0.526
#> 15 76.3 69.5 59.1 0.105
#> 16 66.9 88.9 25.3 0.211
#> 17 20.5 18.0 12.3 0.895
#> 18 35.8 62.9 23.0 0.684
#> 19 35.9 99.0 59.8 0.632
#> 20 69.0 13.0 21.1 0.158
Created on 2022-08-17 by the reprex package (v2.0.1)

Answer 1

You could compose a function to return its input:
rank_function <- function(x) x
Actually this function has been defined in base, i.e. identity.
rank_function <- identity
Also, you can explore the source code of desc:
desc
function (x) -xtfrm(x)
Apparently desc is just the opposite number of xtfrm. So you can use it for ascending ordering.
rank_function <- xtfrm
In the help document of xtfrm(x):
A generic auxiliary function that produces a numeric vector which will sort in the same order as x.