stats

#!/usr/bin/env ruby

class Stats
  def initialize(data)
    @data = data
    @sorted = data.sort
  end

  def size
    @data.size
  end

  def min
    @data.min
  end

  def max
    @data.max
  end

  def mean
    @data.sum(0.0) / size
  end

  def median
    if size.odd?
      @sorted[size/2]
    else
      (@sorted[size/2-1] + @sorted[size/2]) / 2.0
    end
  end

  def median_absolute_deviation(median = median())
    Stats.new(@data.map { |v| (v - median).abs }).median
  end

  def quartile(n)
    return median if n == 2
    index = (n * size) / 4
    @sorted[index]
  end
end

data = STDIN.readlines.map { Float(_1) }
stats = Stats.new(data)
median = stats.median
mad = stats.median_absolute_deviation(median)

puts <<~OUT
median:  #{stats.median}
average: #{stats.mean}
MAD:     #{mad} (#{"%.2f" % (mad / median * 100.0)}%)
min-max: [#{stats.min} - #{stats.max}]
Q1-Q3:   [#{stats.quartile(1)} - #{stats.quartile(3)}]
OUT