Wellford 1 pass method of calculating variance in Go

wellford.go

package main

import (
	"fmt"
	"math"
)

func main() {
	// Find the definition after main
	tracker := WellfordVariance{}

	samples := []float64{
		1.1, 9.1, 2.33, 3.21, -2.3, 1.001, 0.01,
		3.45, 2.28, 4.1, 8.94, 2.1, 3.33, 4.2, 3.2}

	fmt.Println("Sample Data = ", samples)

	// Keep adding elements dynamically
	for _, val := range samples {
		tracker.Add(val)
		if tracker.Deviation() > tracker.M {
			fmt.Printf(
				"\n/!\\ High Deviation Detected - Val = %f, S = %f\n",
				val, tracker.Deviation())
		}
	}

	fmt.Println("\n-- FINISHED")
	fmt.Println("-- Total Samples = ", tracker.count)
	fmt.Printf("-- Mean = %f, Variance = %f, Deviation = %f",
		tracker.Mean(),
		tracker.Variance(),
		tracker.Deviation())

}

/* -- Wellford Variance  -- */

// WellfordVariance - struct to keep track of things dynamically
type WellfordVariance struct {
	count int
	M, S  float64
}

//Add - Dynamic Addition of Values and Keeping Track of Mean & Numerator
func (wv *WellfordVariance) Add(x float64) {
	wv.count = wv.count + 1
	oldM := wv.M
	wv.M += (x - wv.M) / (float64(wv.count))
	wv.S = (x - wv.M) * (x - oldM)
}

// Variance - Return the Variance as of Now !
func (wv *WellfordVariance) Variance() float64 {
	return wv.S
}

// Deviation - Return the Std Deviation as of Now !
func (wv *WellfordVariance) Deviation() float64 {
	return math.Sqrt(wv.S)
}

// Mean - Return the Mean as of Now !
func (wv *WellfordVariance) Mean() float64 {
	return wv.M
}

// Count - Return the count of elements scanned as of Now !
func (wv *WellfordVariance) Count() int {
	return wv.count
}