R/pareto.R

In petershan1119/paretopractice: Set of R Functions for any Usage

#' The probability density function of the pareto distribution.
#'
#' dpareto function evaluates the pdf of pareto dist. at given x with parameters.
#'
#' @param x the point where the pdf to be evaluated
#' @param alpha the shape parameter of pareto dist.
#' @param x_m the scale parameter of pareto dist.
#' @param log.p use log.p = TRUE when you want
#' to get a result in a log scale
#' @return the pdf value of the pareto dist.
#' @examples
#' dpareto(1:5, 2, 3)
#' dpareto(1:5, 2, -3:3)
#' dpareto(1:5, 2:5, 3)
#' @useDynLib paretopractice paretodens
#' @export
dparteo <- function(x, alpha, x_m, log.p = FALSE) {
  if (!is.logical(log.p) || length(log.p) != 1) {
    stop("bad input for argument 'log'")
  }

  input_len <- c(length(x), length(alpha), length(x_m))
  max_len <- max(input_len)

  density <- vector(mode="numeric", length=max_len)

  result <- .C("paretodens",
               as.double(x),
               as.double(alpha),
               as.double(x_m),
               as.integer(input_len),
               as.integer(max_len),
               as.integer(log.p),
               value = as.double(density),
               PACKAGE = "paretopractice")$value
  if (any(is.nan(result))) {
    warning("\n All parameters should be positive.\n NaN is generated.")
  }
  result
}