mad <- function(x, center = median(x), constant = 1.4826,
                na.rm = FALSE, low = FALSE, high = FALSE)
{
    if(na.rm)
	x <- x[!is.na(x)]
    n <- length(x)
    constant *
        if((low || high) && n%%2 == 0) {
            if(low && high) stop("'low' and 'high' cannot be both TRUE")
            n2 <- n %/% 2 + as.integer(high)
            sort(abs(x - center), partial = n2)[n2]
        }
        else median(abs(x - center))
}