Function ExponentialRegression

regression.go:49–81

ExponentialRegression returns an exponential regression on data series

(s Series)

// ExponentialRegression returns an exponential regression on data series
func ExponentialRegression(s Series) (regressions Series, err error) {

	if len(s) == 0 {
		return nil, EmptyInputErr
	}

	var sum [6]float64

	for i := 0; i < len(s); i++ {
		if s[i].Y < 0 {
			return nil, YCoordErr
		}
		sum[0] += s[i].X
		sum[1] += s[i].Y
		sum[2] += s[i].X * s[i].X * s[i].Y
		sum[3] += s[i].Y * math.Log(s[i].Y)
		sum[4] += s[i].X * s[i].Y * math.Log(s[i].Y)
		sum[5] += s[i].X * s[i].Y
	}

	denominator := (sum[1]*sum[2] - sum[5]*sum[5])
	a := math.Pow(math.E, (sum[2]*sum[3]-sum[5]*sum[4])/denominator)
	b := (sum[1]*sum[4] - sum[5]*sum[3]) / denominator

	for j := 0; j < len(s); j++ {
		regressions = append(regressions, Coordinate{
			X: s[j].X,
			Y: a * math.Exp(b*s[j].X),
		})
	}

	return regressions, nil
}

// LogarithmicRegression returns an logarithmic regression on data series
func LogarithmicRegression(s Series) (regressions Series, err error) {