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RCommunityData/R/hhi.R

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# 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)
}