R/select_rename.R

In twolodzko/lolplyr: Adapting dplyr for lists-of-lists

#' Select/rename variables by name
#'
#' \code{select} and \code{rename} methods for lists. The \code{select} method
#' is defined for lists, while when working with objects of other classes it
#' uses dplyr's \code{\link[dplyr]{select}}.
#'
#' @param .data a list.
#' @param \dots one or more unquoted expressions separated by commas.
#'              You can treat variable names like they are positions.
#'              Positive values select variables; negative values to drop
#'              variables. If the first expression is negative, \code{select()}
#'              will automatically start with all variables.
#' @param warn  throw warnings when encountering errors in selecting variables
#'              (\code{FALSE} by default).
#'
#' @seealso \code{\link[dplyr]{select}}, \code{\link[dplyr]{rename}}
#'
#' @examples
#'
#' as_lov(mtcars) %>%
#'   select(mpg, cyl)
#'
#' as_lov(mtcars) %>%
#'   rename(XXX_mpg = mpg)
#'
#' as_lol(mtcars) %>%
#'   select(mpg, cyl) %>%
#'   .[1:5]
#'
#' @export

select_list <- function(.data, ..., warn = TRUE) {
  if (!is_simple_list(.data))
    stop(".data is not a list")
  dots <- quos(...)
  if (length(dots) == 0L)
    return(.data)
  lapply(.data, function(.x) {
    vars <- try_select_vars(names(.x), dots, warn = warn)
    .x[vars]
  })
}

#' @rdname select_list
#' @export

select <- function(.data, ..., warn = TRUE) {
  # this hack is needed as select.list already exists in utils
  if (is_simple_list(.data)) {
    select_list(.data, ..., warn = warn)
  } else {
    dplyr::select(.data, ...)
  }
}

#' @rdname select_list
#' @export

rename.list <- function(.data, ...) {
  dots <- quos(...)
  lapply(.data, function(.x) {
    names(.x) <- names(rename_vars(names(.x), !!! dots,
                                   strict = FALSE))
    .x
  })
}