colwise-mutate.md
In dplyr: A Grammar of Data Manipulation

selection works with grouped data frames (#2624)

Code
  out <- mutate_if(gdf, is.factor, as.character)
Message
  `mutate_if()` ignored the following grouping variables:
  * Column `Species`

colwise verbs deprecate quosures (#4330)

Code
  (expect_warning(mutate_at(mtcars, vars(mpg), quo(mean(.)))))
Output
  <warning/lifecycle_warning_deprecated>
  Warning:
  The `...` argument of `mutate_at()` can't contain quosures as of dplyr 0.8.3.
  i Please use a one-sided formula, a function, or a function name.
Code
  (expect_warning(summarise_at(mtcars, vars(mpg), quo(mean(.)))))
Output
  <warning/lifecycle_warning_deprecated>
  Warning:
  The `...` argument of `summarise_at()` can't contain quosures as of dplyr 0.8.3.
  i Please use a one-sided formula, a function, or a function name.

colwise mutate gives meaningful error messages

Code
  (expect_error(mutate_at(tibble(), "test", ~1)))
Output
  <error/vctrs_error_subscript_oob>
  Error in `tbl_at_vars()`:
  ! Can't subset columns that don't exist.
  x Column `test` doesn't exist.
Code
  tbl <- tibble(gr1 = rep(1:2, 4), gr2 = rep(1:2, each = 4), x = 1:8)
  tbl <- group_by(tbl, gr1)
  (expect_error(summarise_at(tbl, vars(gr1), mean)))
Output
  <error/vctrs_error_subscript_oob>
  Error in `tbl_at_vars()`:
  ! Can't subset columns that don't exist.
  x Column `gr1` doesn't exist.
Code
  (expect_error(mutate_all(mtcars, length, 0, 0)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `mpg = .Primitive("length")(mpg, 0, 0)`.
  Caused by error:
  ! 3 arguments passed to 'length' which requires 1
Code
  (expect_error(mutate_all(mtcars, mean, na.rm = TRUE, na.rm = TRUE)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `mpg = (function (x, ...) ...`.
  Caused by error in `mean.default()`:
  ! formal argument "na.rm" matched by multiple actual arguments