R/fill_na_lag.R

In Sumpfohreule/MyUtilities: Collection of general functions which are useful in multiple contexts

#' Fills NAs within a vector with the last proper value, which came before it
#'
#' NAs which start before any value are left as is.
#' The same goes for vectors only containing NA
#'
#' @param values Any vector
#' @export
fill_na_lag <- function(values) {
  is_na <- is.na(values)
  value_index <- which(!is_na)
  na_index <- which(is_na)
  if (all(length(value_index) != 0, length(na_index) != 0)) {
    na_index <- na_index %>%
      purrr::keep(~ .x > min(value_index))
    replacement_index <- na_index %>%
      purrr::map(~ max(value_index[value_index < .x])) %>%
      unlist()

    values[na_index] <- values[replacement_index]
  }
  return(values)
}