dice.rb

class DiceStats
  attr_accessor :stats, :die

  def initialize(args = {})
    @die    = args[:die] || 6
    @tests  = args[:tests] || [10, 100, 1_000, 10_000, 100_000, 1_000_000]
    @format = args[:format] || generate_default_format
    @stats  = {}

    run_experiments
  end

  def stats_table
    table = "# of Rolls"
    (1..@die).each { |n| table <<  "%8ds" % n }
    table << "\n#{'#' * 66}\n"
    @tests.each { |test| table << format_experiment(test, @stats[test]) }
    table
  end

  private

  def generate_default_format
    "%-12d" + (" | %05.2f%%" * @die) + "\n"
  end

  def format_experiment(total, stats)
    percentages = stats.values.map { |num| (num / total.to_f) * 100 }
    @format % ([ total ] + percentages)
  end

  def run_experiments
    @tests.each do |test|
      run_experiment(test)
    end
    stats
  end

  def run_experiment(size)
    results = new_stats_hash
    size.times do
      roll = roll_dice
      results[roll] += 1
    end
    stats[size] = results
  end

  def new_stats_hash
    (0...@die).inject({}) do |hash,n|
      hash[n] = 0
      hash
    end
  end

  def roll_dice
    rand(@die)
  end
end

dice = DiceStats.new
puts dice.stats_table

output.txt

# of Rolls       1s       2s       3s       4s       5s       6s
##################################################################
10           | 20.00% | 20.00% | 40.00% | 20.00% | 00.00% | 00.00%
100          | 19.00% | 14.00% | 18.00% | 20.00% | 11.00% | 18.00%
1000         | 16.20% | 16.40% | 14.50% | 18.40% | 15.90% | 18.60%
10000        | 16.69% | 17.13% | 15.87% | 16.87% | 16.73% | 16.71%
100000       | 16.73% | 16.58% | 16.83% | 16.70% | 16.73% | 16.43%
1000000      | 16.64% | 16.68% | 16.68% | 16.67% | 16.69% | 16.65%