R/one.R

In OleksF/mytestpackage_R: A Nonsense Package To Test Package Creation

#' Factorial
#'
#' Takes the factorial of a number.
#'
#' @param x a number.
#' @param gamma logical. See details.
#'
#' @details gamma = TRUE designates the factorial function as gamma(x + 1),
#'   where as if FALSE, x! is used. If FALSE, x must be an integer.
#'
#' @export
#'
#' @examples
#' Fac(4.2)
#' Fac(4, gamma = FALSE)
Fac <- function(x, gamma = TRUE){
  if (gamma){
    return(gamma(x + 1))
  } else {
    if (x %% 1 != 0){
      message("If gamma = TRUE, x must be a positive integer. NA returned.")
      return(NA)
    }
    if (x < 0){
      message("If gamma = TRUE, x must be a positive integer. NA returned.")
      return(NA)
    } else if (x == 0 | x == 1){
      return(1)
    } else {
      temp <- x - 1
      while (temp > 1){
        x <- x * temp
        temp <- temp - 1
      }
      return(x)
    }
  }
}


#' X
#'
#' Returns the input.
#'
#' @param x a miscallaneous object
#'
#' @return The miscallaneous object x.
#' @export
#'
#' @examples
#' X(1)
X <- function(x){
  x
}