Mutate a vector within a pipe chain

Question

I'd like to subtract 1 from a vector within a pipe chain. Example, mtcars$mpg.

x <- mtcars
# I don't want to do this:
x %>% mutate(mpg = mpg - 1)

I'm looking for something like this:

x$mpg %>% mutate(. := .-1)

If what I wrote there isn't clear in the second block, I'm trying to write, "take mpg vector then mutate it to be mpg - 1"

Is this possible?

Answer 1

mutate/summarise and other tidyverse functions expects a data.frame as .data. As we are extracting the column values, either use the magrittr helper function subtract

library(magrittr)
x$mpg %>%
     subtract(1)

Or block the code in a {} and then update the column

x$mpg %>%
      {. -1} -> x$mpg

Or use the compound assignment operator (%<>%) for updating the column

head(x$mpg)
#[1] 21.0 21.0 22.8 21.4 18.7 18.1

x$mpg %<>%
          {.- 1}
head(x$mpg)
#[1] 20.0 20.0 21.8 20.4 17.7 17.1