src/library/stats/R/shapiro.test.R

#  File src/library/stats/R/shapiro.test.R
#  Part of the R package, https://www.R-project.org
#
#  Copyright (C) 1995-2012 The R Core Team
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  A copy of the GNU General Public License is available at
#  https://www.R-project.org/Licenses/

shapiro.test <- function(x)
{
    DNAME <- deparse(substitute(x))
    stopifnot(is.numeric(x))
    x <- sort(x[complete.cases(x)])
    n <- length(x)
    if(is.na(n) || n < 3L || n > 5000L)
	stop("sample size must be between 3 and 5000")
    rng <- x[n] - x[1L]
    if(rng == 0) stop("all 'x' values are identical")
    if(rng < 1e-10) x <- x/rng # rescale to avoid ifault=6 with single version.
    res <- .Call(C_SWilk, x)
    RVAL <- list(statistic = c(W = res[1]), p.value = res[2],
		 method = "Shapiro-Wilk normality test", data.name = DNAME)
    class(RVAL) <- "htest"
    return(RVAL)
}