shannon.rb

# SHANNON ENTROPY FUNCTION
def entropy(string)
  entropy = 0
  prob = []
  string.split(//).uniq.each do |c|
    prob << string.count(c).to_f / string.length
  end
  prob.each do |p|
    entropy += p*Math.log(p)/Math.log(2.0)
  end
  -entropy
end