R/chistable.R

In austinragotzy/mathstat: Introduction to Mathematical Statistics R Package

#' @title Chi-Square Distribution
#'
#' @description Presents selected quantiles of the chi-square distribution.
#'
#' @details This table more specifically produces the chi-square distribution table
#' for the \emph{0.01}, \emph{0.025}, \emph{0.050}, \emph{0.100}, \emph{0.900}, \emph{0.950},
#' \emph{0.975}, and \emph{0.990} quantiles. The initial row indicates the selected
#' quantiles and the inital column indicates 'r' degrees of freedom See page 708
#' for more details.
#'
#' @return \code{chistable} is the chi-square distribution table for the selected
#' quantiles.
#'
#' @references Hogg, R., McKean, J., Craig, A. (2018) Introduction to Mathematical
#'             Statistics, 8th Ed. Boston: Pearson.
#'
#' @examples
#' chistable()
#'
#' @export chistable

chistable <- function() {
  
  x <- c(0.01, 0.025, 0.5, 0.1, 0.9, 0.95, 0.975, 0.99)
  
  top <- 30
  
  ptabs <- matrix(rep(0, 240), ncol = 8)
  
  for (i in 1:length(x)) {
    ptabs[, i] <- qchisq(x[i], 1:top)
  }
  
  ptabs <- round(1000 * ptabs)/1000
  chistable <- cbind(1:top, ptabs)
  
  return(chistable)
  
}