#' Compute the sample median.
#' 
#' @param x an object for which a method has been defined, or a numeric
#'      vector containing the values whose median is to be computed.
#' @param na.rm a logical value indicating whether 'NA' values should be
#'      stripped before the computation proceeds.
median <- function (x, na.rm = FALSE) {
    if (is.factor(x) || mode(x) != "numeric") 
        stop("need numeric data")     # TODO: Translate message
    if (na.rm) 
        x <- x[!is.na(x)]
    else if (any(is.na(x))) 
        return(NA)
    n <- length(x)
    if (n == 0) 
        return(NA)
    half <- (n + 1)/2
    if (n%%2 == 1) {
        sort(x, partial = half)[half]
    }
    else {
        sum(sort(x, partial = c(half, half + 1))[c(half, half + 1)])/2
    }
}