如何将列名作为使用 dplyr 的 function 的参数传递，而不将其作为字符串传递？

Question

Here: https://rpubs.com/hadley/dplyr-programming they write the following.

my_summarise <- function(df, group_by) {
  group_by <- enquo(group_by)
  print(group_by)

  df %>%
    group_by(!!group_by) %>%
    summarise(a = mean(a))
}

my_summarise(df, g1)
#> ~g1
#> # A tibble: 2 × 2
#>      g1     a
#>   <dbl> <dbl>
#> 1     1   4.5
#> 2     2   2.0

So I try to copy it, using my idea of a function and my data.

library(MASS)
not.fun <- function(data, column) {
  column <- enquo(column)
  data %>% slice(1:10) %>% select(!!column)
}

not.fun(MASS::Cars93, Length)
Error in select(., !!column) : unused argument (!!column) 

But, guess what, it doesn't work. How to make it work, without using strings? I would be interested in a result possibly done in base R if it'd take as many lines of code to write as a result in some specific package.

Answer 1

The MASS package has it's own select() function. If you load MASS after you load dplyr , you mask the dplyr version of the function. You could be expliclt about which select function you want:

library(MASS)
not.fun <- function(data, column) {
  column <- enquo(column)
  data %>% slice(1:10) %>% dplyr::select(!!column)
}

not.fun(MASS::Cars93, Length)

Answer 2

It is likely to be an issue of function masking as @MrFlick described in his post. If that issue is resolved, instead of the enquo/!! the curly-curly operator can be used {{..}} as well

not.fun <- function(data, column) { 
                    data %>%
                         slice(1:10) %>%
                         dplyr::select({{column}})
   }


not.fun(MASS::Cars93, Length)
#   Length
#1     177
#2     195
#3     180
#4     193
#5     186
#6     189
#7     200
#8     216
#9     198
#10    206