Down and Dirty Stats

dndstats.rb

require 'bigdecimal'
require 'csv'
require 'pp'

class Stats
  include Enumerable

  def initialize(array)
    standardize_array(array)
  end

  def to_csv(file_path)
    file_path ||= "./stats.csv"
    CSV.open(file_path, "w") do |csv|
      csv << ["Results"]
      @array.each do |result|
        csv << [result.to_s("F")]
      end
    end
  end

  def standardize_array(array)
    @array = []
    array.map do |element| 
      if element.class == BigDecimal then next
      elsif element.class == Fixnum then @array << BigDecimal.new(element.to_s)
      elsif element.class == Float then @array << BigDecimal.new(element.to_s)
      elsif element.class == String && element =~ /\A\d+(\.|)\d+\z/ then  @array << BigDecimal.new(element)
      else raise StandardError, "Incompatible elements provided."
      end
    end
  end

  def <<(element)
    @array << element
    standardize_array(@array)
  end

  def sum
    @array.inject(BigDecimal.new("0")) {|memo,item| memo + item }
  end

  def mean
    sum / @array.length
  end

  def sample_variance
    @array.inject(BigDecimal.new("0")) { |memo,element| memo += (element - mean) ** 2 } / BigDecimal.new((@array.length - 1).to_s)
  end

  def standard_deviation
    Math.sqrt(sample_variance)
  end
end