R/cut_r.R

In Keng: Knock Errors Off Nice Guesses

#' Cut-off values of Pearson's correlation r with known sample size n.
#'
#' @param n Sample size of Pearson's correlation r. `n` should be larger than
#'
#' @return A data.frame including the cut-off values of r at the significance levels of p = 0.1, 0.05, 0.01, 0.001.  r with the absolute value larger than the cut-off value is significant at the corresponding significance level.
#' @details
#' Given n and p, t and then r could be determined. The formula used could be found in `test_r()`'s documentation.
#'
#' @export
#'
#' @examples cut_r(193)
cut_r <- function(n) {
  n <- as.integer(n)
  stopifnot(n >= 3)

  p <- c(0.1, 0.05, 0.01, 0.001)
  t <- stats::qt(p = (1 - p/2), df = (n - 2))
  r <- t/sqrt(t^2 + n - 2)
  cbind(p, r)
}