In r-lib/tidyselect: Select from a Set of Strings

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Functions like starts_with(), contains() or matches() are selection helpers that only work in a selection context, e.g. dplyr::select() or the cols argument of tidyr::pivot_longer().

Using a selection helper anywhere else results in an error:

starts_with("foo")

mtcars[contains("foo")]

subset(mtcars, select = matches("foo"))

If you see this error, you may have used a selection helper in the wrong place, possibly as the result of a typo (e.g. misplaced comma or wrong argument name). Alternatively, you may be deliberately trying to reduce duplication in your code by extracting out a selection into a variable:

my_vars <- c(name, species, ends_with("color"))

To make this work you'll need to do two things:

• Wrap the whole thing in a function
• Use any_of() or all_of() instead of bare variable names

my_vars <- function() {
  c(any_of(c("name", "species")), ends_with("color"))
}
dplyr::select(starwars, my_vars())

r-lib/tidyselect documentation built on Dec. 3, 2024, 12:24 p.m.