This Web

All Webs

brayden.org

Books RSS

Random RSS

Software RSS

Other

Parametric Statistics using Ruby

class Stats
  def initialize(aName)
    @name = aName
    self.reset
  end
  attr_reader :name, :maxx, :minx, :n, :sumy, :sumysq, :maxy, :miny
  def reset
    @sumy = @sumysq = 0.0
    @n = 0
    @sumx = @sumxsq = @sumxy = 0.0
    @maxx = @minx = @maxy = @miny =nil
  end
  def mean
    return nil if @n < 1
    return @sumy.to_f / @n
  end
  def variance
    return nil if @n < 2
    ret = @n * @sumysq.to_f - @sumy * @sumy
    return ret /= @n * (@n - 1)
  end
  def stddev
    return nil if @n < 2
    return Math.sqrt(variance)
  end
  def slope
    return nil if @n < 1 || @sumxsq == 0
    return (@n * @sumxy.to_f - @sumx * @sumy) / (@n * @sumxsq - (@sumx * @sumx))
  end
  def intercept
    return nil if @n < 1 || @sumxsq == 0
    return (@sumy - self.slope * @sumx)/@n
  end
  def correlation
    t1 = (@n * @sumxsq.to_f - (@sumx * @sumx)) * (@n * @sumysq - (@sumy * @sumy))
    return (@n * @sumxy - @sumx * @sumy) / Math.sqrt(t1)
  end
  def add(y, *xopt)
    @sumy += y
    @n += 1
    @sumysq += y * y
    @maxy = y if (!@maxy || y > @maxy)
    @miny = y if (!@miny || y < @miny)
    if !xopt || !xopt[0]
      x = @n
    else
      x = xopt[0]
    end
    @sumx += x
    @sumxsq += x * x
    @sumxy += x * y
    @maxx = x if (!@maxx || x > @maxx)
    @minx = x if (!@minx || x < @minx)
    return self
  end
end
if __FILE__ == $0
  def showStats(s)
    puts "#{s.name}----------"
    puts "\tn=#{s.n}\tmean=#{s.mean}\tsigma=#{s.stddev}"
    puts "\tslope=#{s.slope}\tintercept=#{s.intercept}\n\tcorrelation=#{s.correlation}"
  end
  s = Stats.new("Correlation Test")
  s.add(12,3).add(15,4).add(10,2.8).add(20,5.5)
  showStats s
  s = Stats.new("Auto Test")
  s.add(12).add(15).add(20).add(24).add(22).add(28)
  showStats s
  s = Stats.new("Stress Test")
  2000.times { s.add(rand(100)) }
  showStats s
end

-- DaleBrayden - 07 Sep 2002