R/offset-by.R

In hadley/scales: Scale Functions for Visualization

offset_by <- function(x, size) {
  UseMethod("offset_by")
}

#' @export
offset_by.numeric <- function(x, size) {
  x + size
}

#' @export
offset_by.Date <- function(x, size) {
  fun <- function(x) seq(x, length.out = 2, by = size)[2]
  out <- lapply(x, fun)
  do.call(c, out)
}

#' @export
offset_by.POSIXt <- function(x, size) {
  # for subsecond interval support
  # seq() does not support partial secs in character strings
  if (is.character(size) && (parsed <- parse_unit_spec(size))$unit == "sec") {
    fun <- function(x) seq(x, length.out = 2, by = parsed$mult)[2]
  } else {
    fun <- function(x) seq(x, length.out = 2, by = size)[2]
  }
  out <- lapply(x, fun)
  out <- do.call(c, out)
  attr(out, "tzone") <- attr(x, "tzone")
  out
}

#' @export
offset_by.difftime <- function(x, size) {
  if (is.numeric(size)) {
    size_seconds <- size
  } else {
    size_seconds <- unit_seconds(size)
  }

  input_units <- units(x)
  x <- as.numeric(x, units = "secs")

  x <- x + size_seconds

  x <- as.difftime(x, units = "secs")
  units(x) <- input_units

  x
}