R/wilcoxon.pvalues.r

In ejanalysis/batch.summarizer: Summarize Multiple Buffer Reports from the (nonpublic) Batch Tool for EJSCREEN

#' Wilcoxon Signed Rank Test p-values
#'
#' See \url{https://en.wikipedia.org/wiki/Wilcoxon_signed-rank_test}
#' Uses \link{psignrank} function from stats package
#' 
#' @param x List of named quantiles (see example)
#' @param n Sample size (e.g., how many locations)
#' @param digits Default is to round to 4 digits
#'
#' @return Returns p values
#' @export
#'
#' @examples
#'   x <- c(white=0, black=0, native=0, multi=0, minority=9, ling.isol=1, 
#'     age0.4=41, age0.17=0, age65.up=57, no.hs.diploma=41, low.income=48)
#'   # Sample Size (# of facilities w/ 3 mi. population >= 100):
#'   n <- 13
#'   print( wilcoxon.pvalues(x,n) ) 
wilcoxon.pvalues <- function(x,n,digits=4) {
  # from OAR originally
  m <- n*(n + 1)/2
  p.values <- rep(NA, length(x))
  names(p.values) <- names(x)
  if (any(x <= m/2)) { 
    x1 <- which(x <= m/2)
    p.values[x1] <- psignrank(x[x1],n) + (1 - psignrank(m - x[x1],n))
  }
  if (any(x > m/2)) {
    x2 <- which(x > m/2)
    p.values[x2] <- psignrank(m - x[x2], n) + (1 - psignrank(x[x2], n))
  }
  return(round(p.values,digits))
}