R/fill_NA_gaps.R

In JBLecomte/JBUtilities:

#' Fill NA values with previous value in a vector
#'
#' @param x
#' @param firstBack
#'
#' @return
#' @export
fill_NA_gaps <- function(x, firstBack = FALSE) {
  ## NA's in a vector or factor are replaced with last non-NA values
  ## If firstBack is TRUE, it will fill in leading NA's with the first
  ## non-NA value. If FALSE, it will not change leading NA's.

  # If it's a factor, store the level labels and convert to integer
  lvls <- NULL
  if (is.factor(x)) {
    lvls <- levels(x)
    x    <- as.integer(x)
  }

  goodIdx <- !is.na(x)

  # These are the non-NA values from x only
  # Add a leading NA or take the first good value, depending on firstBack
  if (firstBack)   goodVals <- c(x[goodIdx][1], x[goodIdx])
  else             goodVals <- c(NA,            x[goodIdx])

  # Fill the indices of the output vector with the indices pulled from
  # these offsets of goodVals. Add 1 to avoid indexing to zero.
  fillIdx <- cumsum(goodIdx)+1

  x <- goodVals[fillIdx]

  # If it was originally a factor, convert it back
  if (!is.null(lvls)) {
    x <- factor(x, levels=seq_along(lvls), labels=lvls)
  }
  return(x)
}