R/d1f.R

In JackStat/CompPack: Collection of Computational Statistic Tools

#' First Derivative
#' 
#' @description
#' The first derivative of a function evaluated at point(s) x.
#' 
#' Differentiation is a method to compute the rate at which the dependent output (f(x)) changes with respect to the change the independent input (x). The first derrivative can be used to obtain an exact value for the slope of the tangent line, at the point where the derivative was evaluated.
#' 
#' @param f The function that you want to take the derivative of
#' @param x The point or vector of points where the derivative will be evaluated
#' 
#' @author Damon McCafferty \email{damon.mccafferty@@economics.utah.edu}
#' 
#' @examples
#' x = runif(10, pi/3, 3*pi/4)
#' df(tan, x)
#' 
#' @export

d1f <- function(f,x)
{
  d=0.0000001
  (f(x-d)-f(x))/d  
}