"jackknife"<-
function(x, theta, ...)
{
call <- match.call()
        n <- length(x)
        u <- rep(0, n)
        for(i in 1:n) {
                u[i] <- theta(x[ - i], ...)
        }
        thetahat <- theta(x, ...)
        jack.bias <- (n - 1) * (mean(u) - thetahat)
        jack.se <- sqrt(((n - 1)/n) * sum((u - mean(u))^2))
        return(list(jack.se=jack.se, jack.bias=jack.bias, jack.val = u, call=call))
}