R/fct_expand_seq.R

In jmbarbone/jordan: Miscellaneous, Analytic R Kernels

#' Factor Expand by Sequence
#'
#' Expands an ordered factor from one level to another
#'
#' @details Defaults for `min_lvl` and `max_lvl` are the minimum and maximum
#' levels in the ordered vector `x`.
#'
#' @param x An ordered factor
#' @param min_lvl The start of the level sequence
#' @param max_lvl The end of the level sequence
#' @param by Integer, number of steps in between
#' @return An `ordered` vector
#'
#' @examples
#' x <- ordered(letters[c(5:15, 2)], levels = letters)
#' fct_expand_seq(x)
#' fct_expand_seq(x, "g", "s", 3L) # from "g" to "s" by 3
#' fct_expand_seq(x, "g", "t", 3L) # same as above
#'
#' # from the first inherit level to the last observed
#' fct_expand_seq(x, min(levels(x)))
#' @export

fct_expand_seq <- function(
    x,
    min_lvl = min(x, na.rm = TRUE),
    max_lvl = max(x, na.rm = TRUE),
    by = 1L
) {
  stopifnot(
    inherits(x, "ordered"),
    is.integer(by) || by < 1L
  )
  lvls <- levels(x)

  if (is.character(min_lvl) || inherits(min_lvl, "factor")) {
    min_lvl <- which(lvls == min_lvl)
  }

  if (is.character(max_lvl) || inherits(max_lvl, "factor")) {
    max_lvl <- which(lvls == max_lvl)
  }

  if (is.na(min_lvl)) {
    stop(cond_fct_expand_seq_na("min_lvl"))
  }

  if (is.na(max_lvl)) {
    stop(cond_fct_expand_seq_na("max_lvl"))
  }

  int <- seq(from = min_lvl, to = max_lvl, by = by)
  ordered(lvls[int], levels = lvls)
}

# condition ---------------------------------------------------------------

cond_fct_expand_seq_na <- function(x = c("min_lvl", "max_lvl")) {
  x <- match_param(x)
  new_condition(paste(x, "cannot be `NA`"), "fct_expand_seq_na")
}