take histogram with normal-binning and log-binning

histo.rb

require 'pp'

class Histogram

  def self.normal_histo(data)
    histo = Hash.new(0)
    data.each do |d|
      histo[d] += 1
    end
    histo.sort_by {|a| a[0]}
  end

  def self.logbin_histo(data)
    histo = Hash.new(0)
    data.each do |d|
      key = 2 ** (Math.log(d.to_f)/Math.log(2.0)).to_i
      histo[key] += 1
    end
    histo.map {|key,val| [key, val.to_f/key] }.sort_by {|a| a[0]}
  end

  def self.histo_to_s(histo)
    histo.map {|a| a.join(' ')}.join("\n")
  end
end

if $0 == __FILE__
  data = [1,1,1,2,2,3,3,3,4,5,8]
  pp Histogram.normal_histo(data) # => [ [1,3], [2,2], [3,3], [4,1], [5,1], [8,1] ]

  pp Histogram.logbin_histo(data) # => [ [1,3], [2,2.5], [4,0.5], [8,0.125] ]
end