Generate random compositions that sum to <=1

rCompos.R

## Generate random compositions that sum to <=1

library(gtools)
library(ggtern)
library(scatterplot3d)

rCompos <- function(n, subsamples, alphas = NULL){
  if(is.null(alphas)) alphas <- rep(1, subsamples)
  sums <- matrix(runif(n), ncol = 1)
  dirichlet <- gtools::rdirichlet(n, alphas)
  output <- apply(dirichlet, 2, function(x) sums*x)
  return(output)
}

## Generate test data:
mydata <- rCompos(n = 10000, subsamples = 3)
rowSums(mydata)

## Check evenness of sampling across sum component
hist(rowSums(mydata), 100)

## Check evenness of sampling across proportional component
ggtern(data = data.frame(mydata), aes(x=X1, y=X2, z=X3))+
  geom_hex_tern()+
  theme_bw()

## Check evenness of sampling in 3 dimensions
scatterplot3d::scatterplot3d(mydata)
scatterplot3d::scatterplot3d(mydata, angle = 180)