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S4.md

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Introduction

This code calculates indicator S4 of NorInAliS.

Preparations

Define an auxiliary function:

# Combines text strings
"%+%" <- function(string1, string2) paste0(string1, string2)

Input the data for 2016 to 2020:

For the time being, this has to be done manually. Source: [https://view.nina.no/planteimport/]

Data were read from the graph at the tab “Cumulative graphs” with the following parameter choices:

  • one year at a time (2016 to 2020)
  • one taxon at a time (vascular plants and arthropods)
  • “Imported item” = “All”
  • “Export country” = “All”
  • “Data to plot” = “Taxon”
  • “Exclude juveniles” was not ticked
  • “Show only alien species” was ticked
Arthropods <- matrix(
  c(58, 38, 33, 23, 21,
    17, 12, 14, 11, 12),
  2, 5, TRUE,
  list(c("species", "containers"), "yr" %+% 2016:2020))
Plants <- matrix(
  c(33, 26, 22, 16, 11,
    17, 12, 14, 09, 10),
  2, 5, TRUE,
  list(c("species", "containers"), "yr" %+% 2016:2020))

Calculations

Results are standardised for the contents of 10 containers, but are expressed per container.

Output indicator values:

{
  pla <- mean(Plants[1,] / Plants[2,])
  art <- mean(Arthropods[1,] / Arthropods[2,])
  cat("Plants:\n"     %+%
       pla %+% " ± "  %+% (sqrt(pla * 10) / 10) %+% " (mean ± SD)\n\n")
  cat("Arthropods:\n" %+%
       art %+% " ± "  %+% (sqrt(art * 10) / 10) %+% " (mean ± SD)\n\n")
  cat("Totals:\n"     %+% (pla + art) %+% " ± " %+%
                  (sqrt((art + pla) * 10) / 10) %+% " (mean ± SD)\n\n")
  cat("Confidence levels:\n")
  conf <- qpois(c(0.025, 0.25, 0.5, 0.75, 0.975), (art + pla) * 10) / 10
  names(conf) <- c("2.5", "25", "50", "75", "97.5") %+% "% CL"
  print(conf)
}

## Plants:
## 1.71140989729225 ± 0.413691901938175 (mean ± SD)
## 
## Arthropods:
## 2.55529666412019 ± 0.505499422761312 (mean ± SD)
## 
## Totals:
## 4.26670656141244 ± 0.653200318540373 (mean ± SD)
## 
## Confidence levels:
##  2.5% CL   25% CL   50% CL   75% CL 97.5% CL 
##      3.0      3.8      4.2      4.7      5.6