# Community Data Science Collective R Utilities
#
# Copyright (c) 2010-2016 Benjamin Mako Hill and Aaron Shaw 
# mako@atdot.cc, aaronshaw@northwestern.edu

## functions to create normal and non-normalized herfenidahl indexes
hhi <- function (x) {
  x <- x / sum(x)
  sum(x**2)
}

hhi.norm <- function (x) {
  n <- length(x)
  h <- hhi(x)
  (h - 1/n)/(1-1/n)
}