R/discrete_kernel.r

In kernopt: Estimating Count Data Distributions with Discrete Optimal Symmetric Kernel

#' Discrete kernel function
#'
#' @param kernel the type of kernel. Currently supported kernels are limited to:
#'   "optimal", "triang", "epanech" and "binomial"
#' @param x the target point at which the density is calculated
#' @param z the vector of observations
#' @param h the bandwidth (or smoothing parameter)
#' @param k Optional: the integer (positive) parameter that defined the support
#'   of the kernel function (corresponds to parameter 'a' for triangular
#'   kernel). It is only used for optimal and triangular kernel
#' @return Returns the value of the associated kernel function
#' @seealso [discrete_optimal()], [discrete_triang()], [discrete_epanech()],
#'   [discrete_binomial()]  which this function wraps.
#' @export
#'
#' @examples
#' discrete_kernel(kernel = "optimal", x = 25, z = 1:50, h = 0.9, k = 20)
#' discrete_kernel(kernel = "triang", x = 25, z = 1:50, h = 10, k = 20)
#' discrete_kernel(kernel = "epanech", x = 25, z = 1:50, h = 20)
#' discrete_kernel(kernel = "binomial", x = 25, z = 1:50, h = 0.5)
discrete_kernel <- function(kernel = c("optimal", "triang", "epanech", "binomial"),
                            x,
                            z,
                            h,
                            k = NULL) {
  switch(kernel,
    "optimal" = discrete_optimal(
      x = x,
      z = z,
      h = h,
      k = k
    ),
    "triang" = discrete_triang(
      x = x,
      z = z,
      h = h,
      a = k
    ),
    "epanech" = discrete_epanech(x = x, z = z, h = h),
    "binomial" = discrete_binomial(x = x, z = z, h = h)
  )
}