tidyr use glue strings later in function

Question

Tidy eval now supports glue strings

So this works great:

my_summarise5 <- function(data, mean_var ) {
  data %>% 
    mutate(
      "mean_{{mean_var}}" := mean({{ mean_var }}), 
    ) 
}

mtcars %>% my_summarise5(cyl)

But then

my_summarise5 <- function(data, mean_var ) {
  data %>% 
    mutate(
      "mean_{{mean_var}}" := mean({{ mean_var }}), 
    "mean_{{mean_var}}_plusone" :=  "mean_{{mean_var}}"+1
    )
}

mtcars %>% my_summarise5(cyl)

Throws

Error: Problem with `mutate()` input `mean_cyl_plusone`.
x non-numeric argument to binary

Would some 'paste' or 'glue' thing in the "mean_{{mean_var}}_plusone" := "mean_{{mean_var}}"+1 part fix this?

Note this is obviously not a useful case, its a MWE for the syntax. I actually want to define two new columns with different names, one which uses the other ... otherwise I have to repeat and it also gets messy.

Answer 1

Use across:

my_summarise5 <- function(data, mean_var ) {
  data %>% 
    mutate(
      "mean_{{mean_var}}" := mean({{ mean_var }}),
      across(last_col(), ~.+1, .names = "{col}_plusone")
    )
}

mtcars %>% my_summarise5(cyl) %>% head

giving:

                   mpg cyl disp  hp drat    wt  qsec vs am gear carb mean_cyl mean_cyl_plusone
Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4   6.1875           7.1875
Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4   6.1875           7.1875
Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1   6.1875           7.1875
Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1   6.1875           7.1875
Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2   6.1875           7.1875
Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1   6.1875           7.1875