gastwirth estimator, weighted median

Gastwirth.R

gastwirth <- function(x,...){
  # gastwirth's location estimator
  # discussed in Ronald Pearson's Exploring Data in Engineering, the Sciences, and Medicine
  # and at http://exploringdatablog.blogspot.com/2012/03/gastwirths-location-estimator.html
  ordstats = quantile(x, probs=c(1/3,1/2,2/3),...)
  weights = c(0.3,0.4,0.3)
  sum(weights*ordstats)
  #
}


wmedian <- function(x, weights, na.rm = FALSE) {
    if (missing(weights)) 
        weights <- rep.int(1, length(x)) else {
        if (any(is.na(weights))) 
            stop("Weights cannot contain NA")
        if (length(weights) != length(x)) 
            stop("weights not same length as values")
        if (any(weights < 0)) 
            stop("Weights must be non-negative")
    }
    if (is.integer(weights)) 
        weights <- as.numeric(weights)
    if (na.rm) {
        weights <- weights[i <- !is.na(x)]
        x <- x[i]
    }
    if (all(weights == 0)) {
        warning("Weights are all zero")
        return(NA)
    }
    x <- x[order(x)]
    weights <- weights[order(x)]
    p <- cumsum(weights)/sum(weights)
    n <- sum(p < 0.5)
    if (p[n + 1] > 0.5) 
        x[n + 1] else (x[n + 1] + x[n + 2])/2
}