Adding upstream version 2.1.2.

Signed-off-by: Daniel Baumann <daniel@debian.org>

linear_coefficient_provider.go

@@ -0,0 +1,42 @@
+package chart
+
+// LinearCoefficientProvider is a type that returns linear cofficients.
+type LinearCoefficientProvider interface {
+	Coefficients() (m, b, stdev, avg float64)
+}
+
+// LinearCoefficients returns a fixed linear coefficient pair.
+func LinearCoefficients(m, b float64) LinearCoefficientSet {
+	return LinearCoefficientSet{
+		M: m,
+		B: b,
+	}
+}
+
+// NormalizedLinearCoefficients returns a fixed linear coefficient pair.
+func NormalizedLinearCoefficients(m, b, stdev, avg float64) LinearCoefficientSet {
+	return LinearCoefficientSet{
+		M:      m,
+		B:      b,
+		StdDev: stdev,
+		Avg:    avg,
+	}
+}
+
+// LinearCoefficientSet is the m and b values for the linear equation in the form:
+// y = (m*x) + b
+type LinearCoefficientSet struct {
+	M      float64
+	B      float64
+	StdDev float64
+	Avg    float64
+}
+
+// Coefficients returns the coefficients.
+func (lcs LinearCoefficientSet) Coefficients() (m, b, stdev, avg float64) {
+	m = lcs.M
+	b = lcs.B
+	stdev = lcs.StdDev
+	avg = lcs.Avg
+	return
+}