PlotRarefaction(
  comparison.list,
  y.axis = "Statistic",
  x.axis = "Number of sampled specimens"
)

## Not run:  
ind.data <- iris[1:50,1:4]

results.RS <- Rarefaction(ind.data, PCAsimilarity, num.reps = 5)
results.Mantel <- Rarefaction(ind.data, MatrixCor, correlation = TRUE, num.reps = 5)
results.KrzCov <- Rarefaction(ind.data, KrzCor, num.reps = 5)
results.PCA <- Rarefaction(ind.data, PCAsimilarity, num.reps = 5)

#Plotting using ggplot2
a <- PlotRarefaction(results.RS, "Random Skewers")
b <- PlotRarefaction(results.Mantel, "Mantel")
c <- PlotRarefaction(results.KrzCov, "KrzCor")
d <- PlotRarefaction(results.PCA, "PCAsimilarity")

library(cowplot)
plot_grid(a, b, c, d, labels = c("RS", 
                                 "Mantel Correlation", 
                                 "Krzanowski Correlation", 
                                 "PCA Similarity"), 
                      scale = 0.9)

## End(Not run)