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Contents
module Enumerable
# Returns the maximum possible Shannon entropy of the array
# with given size assuming that it is an "order-0" source
# (each element is selected independently of the next).
#
#
#
#--
# Credit goes to Derek.
#++
def ideal_entropy
arr = self.to_a
unitProb = 1.0.to_f / arr.size.to_f
(-1.to_f * arr.size.to_f * unitProb * Math.log(unitProb)/Math.log(2.to_f))
end
end
# Not needed b/c ideal_entropy is only dependent on size.
# class String
# def ideal_entropy
# self.split(//).ideal_entropy
# end
# end
# _____ _
# |_ _|__ ___| |_
# | |/ _ \/ __| __|
# | | __/\__ \ |_
# |_|\___||___/\__|
#
=begin test
require 'test/unit'
class TCEnumerable < Test::Unit::TestCase
def test_ideal_entropy
assert_equal( 1.0, %w{ a b }.ideal_entropy )
assert_equal( 2.0, %w{ a a b b }.ideal_entropy )
end
end
=end
Version data entries
26 entries across 26 versions & 1 rubygems