R/ellipse-perimeter.R

In razaboysdata/ellipse:

#' Calculate the length of the perimeter of an ellipse.
#' @ imporrt from pracma
#' @param r Length of the semi-major axis.
#' @param e The eccentricity.
#' @return The length of the perimeter of the ellipse with specified semi-major axis and eccentricity.
#' @examples
#' ellipse_perimeter(1, 1)
#'
#' @export
ellipse_perimeter <- function(r, e = 0) {
  if (e < 0 || e > 1) stop("Invalid eccentricity!", call. = FALSE)
  if (r <= 0) stop ("Invalid semi major axis", call. = FALSE)
  if (e == 0) { 2 * pi * r
    }
 else {
    4 * r * pracma::ellipke(e)$e
  }
}

#always check if the user gives sane values.