R/hypotenuse.R

In richierocks/learningr: Data and Functions to Accompany the Book "Learning R"

#' Dumb hypotenuse function.
#' 
#' Calculate the (Pythagorean) hypotenuse of two numeric vectors
#' using the obvious algorithm.
#' @param x A numeric vector.
#' @param y A numeric vector.
#' @return A numeric vector of the hyptenuse of the inputs.
#' @note This algorithm fails when the inputs are very large of very small, 
#' making it unsuitable for real-world use.
#' @references Cleve Moler (MATLAB creator and discoverer of the Moler-Morrison
#' algorithm for calculating hypotenuses) discusses the pro and cons
#' of several algorithms here.
#' \url{http://blogs.mathworks.com/cleve/2012/07/30/pythagorean-addition}
#' @seealso \code{\link[pracma]{hypot}}
#' @examples
#' hypotenuse(5, 12)           #okay
#' hypotenuse(1e-300, 1e-300)  #fails
#' hypotenuse(1e300, 1e300)    #fails
#' @export
hypotenuse <- function(x, y)
{
  sqrt(x ^ 2 + y ^ 2)
}