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// Copyright 2010 Petar Maymounkov. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package llrb
import "math"
// avgVar maintains the average and variance of a stream of numbers
// in a space-efficient manner.
type avgVar struct {
count int64
sum, sumsq float64
}
func (av *avgVar) Init() {
av.count = 0
av.sum = 0.0
av.sumsq = 0.0
}
func (av *avgVar) Add(sample float64) {
av.count++
av.sum += sample
av.sumsq += sample * sample
}
func (av *avgVar) GetCount() int64 { return av.count }
func (av *avgVar) GetAvg() float64 { return av.sum / float64(av.count) }
func (av *avgVar) GetTotal() float64 { return av.sum }
func (av *avgVar) GetVar() float64 {
a := av.GetAvg()
return av.sumsq/float64(av.count) - a*a
}
func (av *avgVar) GetStdDev() float64 { return math.Sqrt(av.GetVar()) }
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