R like stats, command line style

rlikestats

#!/usr/bin/env ruby
#
# Now living in https://github.com/mat/dotfiles
#

class Rlikestats

  attr_accessor :values, :count, :mean, :stdev, :lines

  def initialize
    self.values = []
    self.count = 0
    self.mean  = 0.0
    self.lines = 0
  end

  def run
    m2 = 0.0
    while line = $stdin.gets
      self.lines += 1
      unless line =~ /^\d/
        $stderr.puts "Skipping line #{lines}: #{line}"
        next
      end
      self.count += 1
      val = line.to_f
      values << val

      delta = val - self.mean
      self.mean += delta / count
      m2 = m2 + delta * (val - self.mean)
    end
    variance = m2 / (self.count - 1)
    self.stdev = Math.sqrt(variance)

    values.sort!
    print_result
  end

  def percentile(pct)
    values[(count * pct).floor]
  end

  def print_result
    puts "#Values  :  %12d"   % values.size
    puts "Min      :  %12.4f" % values.first
    puts "1st Qu.  :  %12.4f" % percentile(0.25)
    puts "Median   :  %12.4f" % percentile(0.50)
    puts "Mean     :  %12.4f" % mean
    puts "Stdev    :  %12.4f" % stdev
    puts "3rd Qu.  :  %12.4f" % percentile(0.75)
    puts "90th Pct.:  %12.4f" % percentile(0.90)
    puts "Max      :  %12.4f" % values.last
  end
end

Rlikestats.new.run