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#' Select variables from character vectors
#'
#' @description
#'
#' These [selection helpers][language] select variables
#' contained in a character vector. They are especially useful for
#' programming with selecting functions.
#'
#' * [all_of()] is for strict selection. If any of the variables in
#' the character vector is missing, an error is thrown.
#'
#' * [any_of()] doesn't check for missing variables. It is especially
#' useful with negative selections, when you would like to make sure
#' a variable is removed.
#'
#' The order of selected columns is determined by the order in the
#' vector.
#'
#' @inheritParams starts_with
#' @param x A vector of character names or numeric locations.
#'
#' @section Examples:
#'
#' ```{r, child = "man/rmd/setup.Rmd"}
#' ```
#'
#' Selection helpers can be used in functions like `dplyr::select()`
#' or `tidyr::pivot_longer()`. Let's first attach the tidyverse:
#'
#' ```{r, comment = "#>", collapse = TRUE}
#' library(tidyverse)
#'
#' # For better printing
#' iris <- as_tibble(iris)
#' ```
#'
#' It is a common to have a names of variables in a vector.
#'
#' ```{r, comment = "#>", collapse = TRUE}
#' vars <- c("Sepal.Length", "Sepal.Width")
#'
#' iris[, vars]
#' ```
#'
#' To refer to these variables in selecting function, use `all_of()`:
#'
#' ```{r, comment = "#>", collapse = TRUE}
#' iris %>% select(all_of(vars))
#'
#' iris %>% pivot_longer(all_of(vars))
#' ```
#'
#' If any of the variable is missing from the data frame, that's an error:
#'
#' ```{r, error = TRUE}
#' starwars %>% select(all_of(vars))
#' ```
#'
#' Use `any_of()` to allow missing variables:
#'
#' ```{r, comment = "#>", collapse = TRUE}
#' starwars %>% select(any_of(vars))
#' ```
#'
#' `any_of()` is especially useful to remove variables from a data
#' frame because calling it again does not cause an error:
#'
#' ```{r, comment = "#>", collapse = TRUE}
#' iris %>% select(-any_of(vars))
#'
#' iris %>% select(-any_of(vars)) %>% select(-any_of(vars))
#' ```
#'
#' @seealso `r rd_helpers_seealso()`
#' @export
all_of <- function(x) {
if (is.function(x)) {
# Trigger bad type error
vctrs::vec_as_location(x, 0L)
abort("Internal error: `all_of()` should have failed sooner")
}
x
}
#' @rdname all_of
#' @inheritParams ellipsis::dots_empty
#' @export
any_of <- function(x, ..., vars = NULL) {
vars <- vars %||% peek_vars(fn = "any_of")
ellipsis::check_dots_empty()
as_indices_impl(x, vars = vars, strict = FALSE)
}
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