AMR/R/skewness.R

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# ==================================================================== #
# TITLE #
# Antimicrobial Resistance (AMR) Analysis #
# #
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# SOURCE #
# https://gitlab.com/msberends/AMR #
# #
# LICENCE #
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# (c) 2019 Berends MS (m.s.berends@umcg.nl), Luz CF (c.f.luz@umcg.nl) #
# #
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# This R package is free software; you can freely use and distribute #
# it for both personal and commercial purposes under the terms of the #
# GNU General Public License version 2.0 (GNU GPL-2), as published by #
# the Free Software Foundation. #
# #
# This R package was created for academic research and was publicly #
# released in the hope that it will be useful, but it comes WITHOUT #
# ANY WARRANTY OR LIABILITY. #
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# Visit our website for more info: https://msberends.gitlab.io/AMR. #
# ==================================================================== #
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#' Skewness of the sample
#'
#' @description Skewness is a measure of the asymmetry of the probability distribution of a real-valued random variable about its mean.
#'
#' When negative: the left tail is longer; the mass of the distribution is concentrated on the right of the figure. When positive: the right tail is longer; the mass of the distribution is concentrated on the left of the figure.
#' @param x a vector of values, a [`matrix`] or a [`data.frame`]
#' @param na.rm a logical value indicating whether `NA` values should be stripped before the computation proceeds.
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#' @exportMethod skewness
#' @seealso [kurtosis()]
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#' @rdname skewness
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#' @inheritSection AMR Read more on our website!
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#' @export
skewness <- function(x, na.rm = FALSE) {
UseMethod("skewness")
}
#' @exportMethod skewness.default
#' @rdname skewness
#' @export
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skewness.default <- function(x, na.rm = FALSE) {
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x <- as.vector(x)
if (na.rm == TRUE) {
x <- x[!is.na(x)]
}
n <- length(x)
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(base::sum((x - base::mean(x))^3) / n) / (base::sum((x - base::mean(x)) ^ 2) / n) ^ (3 / 2)
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}
#' @exportMethod skewness.matrix
#' @rdname skewness
#' @export
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skewness.matrix <- function(x, na.rm = FALSE) {
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base::apply(x, 2, skewness.default, na.rm = na.rm)
}
#' @exportMethod skewness.data.frame
#' @rdname skewness
#' @export
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skewness.data.frame <- function(x, na.rm = FALSE) {
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base::sapply(x, skewness.default, na.rm = na.rm)
}