kurtosis, skewness, start with ML

R/kurtosis.R

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+#' Kurtosis of the sample
+#'
+#' @description Kurtosis is a measure of the "tailedness" of the probability distribution of a real-valued random variable.
+#'
+#' @param x a vector of values, a \code{matrix} or a \code{data frame}
+#' @param na.rm a logical value indicating whether \code{NA} values should be stripped before the computation proceeds.
+#' @exportMethod kurtosis
+#' @seealso \code{\link{skewness}}
+#' @rdname kurtosis
+#' @export
+kurtosis <- function(x, na.rm = FALSE) {
+  UseMethod("kurtosis")
+}
+
+#' @exportMethod kurtosis.default
+#' @rdname kurtosis
+#' @export
+kurtosis.default <- function (x, na.rm = FALSE) {
+  x <- as.vector(x)
+  if (na.rm == TRUE) {
+    x <- x[!is.na(x)]
+  }
+  n <- length(x)
+  n * base::sum((x - base::mean(x, na.rm = na.rm))^4, na.rm = na.rm) /
+    (base::sum((x - base::mean(x, na.rm = na.rm))^2, na.rm = na.rm)^2)
+}
+
+#' @exportMethod kurtosis.matrix
+#' @rdname kurtosis
+#' @export
+kurtosis.matrix <- function (x, na.rm = FALSE) {
+  base::apply(x, 2, kurtosis.default, na.rm = na.rm)
+}
+
+#' @exportMethod kurtosis.data.frame
+#' @rdname kurtosis
+#' @export
+kurtosis.data.frame <- function (x, na.rm = FALSE) {
+  base::sapply(x, kurtosis.default, na.rm = na.rm)
+}