R/xfromz.R

In JVAdams/artiFISHal: A Pelagic Fish Community Simulator

#' Determine Easting from Bottom Depth
#'
#' Determine the easting from a given distance to lake bottom,
#' incorporating random assignment to west or east shore if not specified.
#' @param z
#'   A numeric vector of the distances to lake bottom to convert (in m).
#' @param maxz
#'   A numeric scalar, the maximum bottom depth of the lake (in m).
#' @param ints
#'   A numeric vector of length 2, the intercepts of the angled lake beds along
#'   the west and east shores of the lake (in m).
#' @param slopes
#'   A numeric vector of length 2, the slopes of the angled lake beds along
#'   the west and east shores of the lake (unitless).
#' @param shore
#'   A numeric or character scalar, indicating if the shore should be west (0),
#'   east (1) or randomly assigned ("random", default).
#' @return
#'   A numeric vector, same length as \code{x}, with distances to bottom for
#'   each easting provided (in m).
#' @export
#' @details
#'   An internal function called by \code{\link{SimFish}}.
#' @seealso
#'   \code{\link{SimFish}}, \code{\link{dfromx}}, \code{\link{zfromx}}.
#'   The assignment to shore is necessary because the artificial lake will have
#'   two eastings for each bottom depth (except for the depth at the vertex).

xfromz <- function(z, maxz, ints, slopes, shore="random") {
  x <- rep(NA, length(z))
  side <- if (shore[1]=="random") {
    sample(0:1, length(z), replace=TRUE)
  } else {
    shore
  }
  x[!is.na(z) & side==0] <- (z[!is.na(z) & side==0] - ints[1]) / slopes[1]
  x[!is.na(z) & side==1] <- (z[!is.na(z) & side==1] - ints[2]) / slopes[2]
  x[z >= maxz] <- runif(sum(z >= maxz), (maxz - ints[1]) / slopes[1],
    (maxz - ints[2]) / slopes[2])
  x
}