I have a very simple need on a data frame with large number of numeric columns. I want to round down all numeric values to one decimal max, but exclude one specific column by name or position or whatever from this rounding.

For example, in this case, I don’t want drat column to be rounded down, let us say.

mtcars %>% mutate_if(is.numeric, round, 1)

How can I do this, without having enumerate all columns? BTW – my data has non-numeric columns too, and so mutate_if sounds right.

>Solution :

Use mutate/across as shown. drat can be replaced with 5 if desired since drat is the fifth column. If we had ix <- "drat" or ix <- 5 then replace drat with all_of(ix) .

library(dplyr)
mtcars %>% mutate(across(where(is.numeric) & !drat, ~ round(.x, 1)))

giving

                     mpg cyl  disp  hp drat  wt qsec vs am gear carb
Mazda RX4           21.0   6 160.0 110 3.90 2.6 16.5  0  1    4    4
Mazda RX4 Wag       21.0   6 160.0 110 3.90 2.9 17.0  0  1    4    4
Datsun 710          22.8   4 108.0  93 3.85 2.3 18.6  1  1    4    1
...snip...