17 lines
319 B
Ruby
17 lines
319 B
Ruby
require 'facets/math/theil_index'
|
|
|
|
module Math
|
|
|
|
# Closely related to the Theil index and easily expressible
|
|
# in terms of it.
|
|
#
|
|
# AI = 1-e^{theil_index}
|
|
#
|
|
# http://en.wikipedia.org/wiki/Atkinson_index
|
|
def self.atkinson_index(array)
|
|
t = theil_index(array)
|
|
(t < 0) ? -1 : 1-Math::E**(-t)
|
|
end
|
|
|
|
end
|