How to calculate ecd

[joethorley]

In small sample size bias vignette it is as follows:

Ag$ecdf <- (rank(Ag$Conc)+.25)/(nrow(Ag)+.5)

which gives

# A tibble: 9 × 6
  Chemical Species                Conc Group        Units  ecdf
  <chr>    <chr>                 <dbl> <fct>        <chr> <dbl>
1 Silver   Oncorhynchus mykiss    0.24 Fish         ug/L  0.132
2 Silver   Lemna gibba            0.63 Plant        ug/L  0.237
3 Silver   Ceriodaphnia dubia     0.78 Invertebrate ug/L  0.342
4 Silver   Pimephales promelas    0.83 Fish         ug/L  0.447
5 Silver   Ictalurus punctatus    1.9  Fish         ug/L  0.553
6 Silver   Daphnia magna          2.12 Invertebrate ug/L  0.658
7 Silver   Hyalella azteca        4    Invertebrate ug/L  0.763
8 Silver   Chironomus tentans    13    Invertebrate ug/L  0.868
9 Silver   Micropterus salmoides 23    Fish         ug/L  0.974

[1] 0.1315789 0.2368421 0.3421053 0.4473684 0.5526316 0.6578947 0.7631579 0.8684211 0.9736842

but in the functions it is

function(x, ties.method = "first") {
  (rank(x, ties.method = ties.method) - 0.5) / length(x)
}

which gives

[1] 0.05555556 0.16666667 0.27777778 0.38888889 0.50000000 0.61111111 0.72222222 0.83333333 0.94444444