Demonstration of a Chinese Restaurant Process, with an optional parameter to push the tables towards a uniform distribution rather than dirichlet (i.e. preferential attachment)

chinese restuarant process.R

# chinese restuarant process
chinese_restaurant = function(n, uniform=FALSE){
  tables = c(1) # running counts of people at tables. Start by seating first person at their own table
  U = runif(n)
  for (i in 2:n){
    if(U[i]<1/i){
      tables = c(tables, 1)
    } else {
      p = tables/(i) # sum(tables) = i-1
      
      # Invert probabilities for more uniform allocation
      if (uniform & (length(p)>1)) p = 1-p
      
      ix = sample(length(tables), 1, prob=p)
      tables[ix] = tables[ix]+1
    }
  }
  tables
}

sort(chinese_restaurant(1e2), decreasing=TRUE)
sort(chinese_restaurant(1e4, uniform=TRUE), decreasing=TRUE)