gistfile1.txt

gini <- function(x, unbiased = TRUE, na.rm = FALSE){
    if (!is.numeric(x)){
        warning("'x' is not numeric; returning NA")
        return(NA)
    }
    if (!na.rm && any(na.ind <- is.na(x)))
        stop("'x' contain NAs")
    if (na.rm)
        x <- x[!na.ind]
    n <- length(x)
    mu <- mean(x)
    N <- if (unbiased) n * (n - 1) else n * n
    ox <- x[order(x)]
    dsum <- drop(crossprod(2 * 1:n - n - 1,  ox))
    dsum / (mu * N)
}

> gini(rpareto(1000, 5, 4))
[1] 0.5422903
> gini(rpareto(1000, 5, 5))
[1] 0.5621999
> conc(rpareto(1000, 5, 4))
[1] 0.002452469
> conc(rpareto(1000, 5, 5))
[1] 0.002726071