def sample( s )
      @sum += s
      @sumsq += s * s
      if @num == 0
        @min = @max = s
      else
        @min = s if @min > s
        @max = s if @max < s
      end
      @num += 1
      @last = s
    end
def sample( s )
      @sum += s
      @sumsq += s * s
      if @num == 0
        @min = @max = s
      else
        @min = s if @min > s
        @max = s if @max < s
      end
      @num += 1
      @last = s
    end
Adds a sampling to the calculations.