SS_readwtatage.R

#' Read in a weight-at-age data file as a data frame
#'
#' @template file
#' @template verbose
#' @export
#' @return Returns a data frame with a variable number of columns based on the
#' number of ages that are included in the file. Though, the first columns
#' will always be `Yr`, `Seas`, `Sex`, `Bio_Pattern`, `BirthSeas`, and `Fleet`.
#' The seventh column will be age zero.
#' The last or next to last column will be the maximum age included
#' in the weight-at-age data. For Stock Synthesis versions 3.30 and greater,
#' the last column will be a column of comments.
#'
#' `NULL` is returned if `file` does not exist or if the file does exist but
#' it is empty. This behavior is different than other `SS_read*` functions that
#' error if either of the previous checks are `TRUE`. Thus, a complicated check
#' involving [tryCatch()] is used around [readLines()] to allow for returning
#' `NULL` rather than `stop()`. Additionally, this check accommodates a URL
#' for `file`.
#' @author Kelli F. Johnson, Ian G. Taylor
#'
SS_readwtatage <- function(file = "wtatage.ss", verbose = TRUE) {
  test <- tryCatch(
    expr = readLines(file),
    error = function(x) "No file",
    warning = function(x) "No file"
  )
  if (test[1] == "No file" | length(test) <= 2) {
    if (verbose) {
      message("Skipping weight-at-age file. File missing or empty: ", file)
    }
    return(NULL)
  }

  # read full file
  wtatagelines <- read.table(file,
    header = FALSE,
    comment.char = "#",
    blank.lines.skip = TRUE,
    stringsAsFactors = FALSE,
    strip.white = TRUE,
    fill = TRUE
  )
  # check for NA is first 2 rows of 2nd column as indicator of version
  # prior to 3.30 where old models had additional number of lines input
  skip <- 1
  if (all(is.na(wtatagelines[1:2, 2])) & !is.na(wtatagelines[3, 2])) {
    # number of lines input is not actually used in this function
    # but included here just to clarify what that first row contains
    Nlines <- wtatagelines[1, 1]
    skip <- 2
  }
  # get max age on 1st line for 3.30, 2nd line for 3.24
  accuage <- wtatagelines[skip, 1]
  # remainder of table skipping first 1 or 2 lines
  wtatage <- wtatagelines[-(1:skip), ]
  # problems with header so simply manually replacing column names
  wtatage_names <- c(
    "Yr", "Seas", "Sex", "Bio_Pattern", "BirthSeas", "Fleet",
    0:accuage
  )
  # new comment line in 3.30
  if (ncol(wtatage) == length(wtatage_names) + 1) {
    wtatage_names <- c(wtatage_names, "comment")
  }
  names(wtatage) <- wtatage_names
  # Remove terminator line
  wtatage <- wtatage[wtatage[["Yr"]] > -9998, ]
  return(wtatage)
}