bootstrap <- function(data, n_reps) {

  results <- numeric(n_reps)

  n <- nrow(data)

  i <- matrix(sample(n, n * n_reps, replace = TRUE), n_reps, n)

  freqs <- t(apply(i, 1, tabulate, ncol(i)))

  for (rep in seq_len(n_reps)) {

    samp <- freqs[rep, ]

    jac <- JS(data, samp)

    results[rep] <- mean(jac)

  }

  return(results)

}

#' @importFrom vegan vegdist

JS <- function(data, indices) {

  d <- data[indices, ]

  jac <- vegan::vegdist(d, method = "jaccard")

  jac1 <- 1 - jac

  return(mean(jac1))

}