code: func (h *WeightedHistogram) CDF(x float64) float64 {
  	count := 0.0
  	for i := range h.bins {
  		if h.bins[i].value <= x {
  			count += float64(h.bins[i].count)
  		}
  	}
  
  	return count / h.total
  }
docs: // CDF returns the value of the cumulative distribution function
  // at x