Sha256: 8ef19111b1eed4b93bafbdd55ceeac9d1c467b6e28bd9988a430e52d28ce8953
Contents?: true
Size: 975 Bytes
Versions: 22
Compression:
Stored size: 975 Bytes
Contents
#--
# Credit goes to Derek.
#++
require 'facet/enumerable/ideal_entropy'
require 'facet/enumerable/probability'
module Enumerable
# Shannon's entropy for an array - returns the average
# bits per symbol required to encode the array.
# Lower values mean less "entropy" - i.e. less unique
# information in the array.
#
# %w{ a b c d e e e }.entropy #=>
#
def entropy
arr = self.to_a
probHash = arr.probability
# h is the Shannon entropy of the array
h = -1.to_f * probHash.keys.inject(0.to_f) do |sum, i|
sum + (probHash[i] * (Math.log(probHash[i])/Math.log(2.to_f)))
end
h
end
end
class String
def entropy
self.split(//).entropy
end
end
# _____ _
# |_ _|__ ___| |_
# | |/ _ \/ __| __|
# | | __/\__ \ |_
# |_|\___||___/\__|
#
=begin test
require 'test/unit'
class TCEnumerable < Test::Unit::TestCase
def test_entropy
assert_equal( 1.0, %w{ a b }.entropy )
end
end
=end
Version data entries
22 entries across 22 versions & 1 rubygems