Adding upstream version 2.1.2.

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

polynomial_regression_series.go

@@ -0,0 +1,177 @@
+package chart
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/wcharczuk/go-chart/v2/matrix"
+)
+
+// Interface Assertions.
+var (
+	_ Series              = (*PolynomialRegressionSeries)(nil)
+	_ FirstValuesProvider = (*PolynomialRegressionSeries)(nil)
+	_ LastValuesProvider  = (*PolynomialRegressionSeries)(nil)
+)
+
+// PolynomialRegressionSeries implements a polynomial regression over a given
+// inner series.
+type PolynomialRegressionSeries struct {
+	Name  string
+	Style Style
+	YAxis YAxisType
+
+	Limit       int
+	Offset      int
+	Degree      int
+	InnerSeries ValuesProvider
+
+	coeffs []float64
+}
+
+// GetName returns the name of the time series.
+func (prs PolynomialRegressionSeries) GetName() string {
+	return prs.Name
+}
+
+// GetStyle returns the line style.
+func (prs PolynomialRegressionSeries) GetStyle() Style {
+	return prs.Style
+}
+
+// GetYAxis returns which YAxis the series draws on.
+func (prs PolynomialRegressionSeries) GetYAxis() YAxisType {
+	return prs.YAxis
+}
+
+// Len returns the number of elements in the series.
+func (prs PolynomialRegressionSeries) Len() int {
+	return MinInt(prs.GetLimit(), prs.InnerSeries.Len()-prs.GetOffset())
+}
+
+// GetLimit returns the window size.
+func (prs PolynomialRegressionSeries) GetLimit() int {
+	if prs.Limit == 0 {
+		return prs.InnerSeries.Len()
+	}
+	return prs.Limit
+}
+
+// GetEndIndex returns the effective limit end.
+func (prs PolynomialRegressionSeries) GetEndIndex() int {
+	windowEnd := prs.GetOffset() + prs.GetLimit()
+	innerSeriesLastIndex := prs.InnerSeries.Len() - 1
+	return MinInt(windowEnd, innerSeriesLastIndex)
+}
+
+// GetOffset returns the data offset.
+func (prs PolynomialRegressionSeries) GetOffset() int {
+	if prs.Offset == 0 {
+		return 0
+	}
+	return prs.Offset
+}
+
+// Validate validates the series.
+func (prs *PolynomialRegressionSeries) Validate() error {
+	if prs.InnerSeries == nil {
+		return fmt.Errorf("linear regression series requires InnerSeries to be set")
+	}
+
+	endIndex := prs.GetEndIndex()
+	if endIndex >= prs.InnerSeries.Len() {
+		return fmt.Errorf("invalid window; inner series has length %d but end index is %d", prs.InnerSeries.Len(), endIndex)
+	}
+
+	return nil
+}
+
+// GetValues returns the series value for a given index.
+func (prs *PolynomialRegressionSeries) GetValues(index int) (x, y float64) {
+	if prs.InnerSeries == nil || prs.InnerSeries.Len() == 0 {
+		return
+	}
+
+	if prs.coeffs == nil {
+		coeffs, err := prs.computeCoefficients()
+		if err != nil {
+			panic(err)
+		}
+		prs.coeffs = coeffs
+	}
+
+	offset := prs.GetOffset()
+	effectiveIndex := MinInt(index+offset, prs.InnerSeries.Len())
+	x, y = prs.InnerSeries.GetValues(effectiveIndex)
+	y = prs.apply(x)
+	return
+}
+
+// GetFirstValues computes the first poly regression value.
+func (prs *PolynomialRegressionSeries) GetFirstValues() (x, y float64) {
+	if prs.InnerSeries == nil || prs.InnerSeries.Len() == 0 {
+		return
+	}
+	if prs.coeffs == nil {
+		coeffs, err := prs.computeCoefficients()
+		if err != nil {
+			panic(err)
+		}
+		prs.coeffs = coeffs
+	}
+	x, y = prs.InnerSeries.GetValues(0)
+	y = prs.apply(x)
+	return
+}
+
+// GetLastValues computes the last poly regression value.
+func (prs *PolynomialRegressionSeries) GetLastValues() (x, y float64) {
+	if prs.InnerSeries == nil || prs.InnerSeries.Len() == 0 {
+		return
+	}
+	if prs.coeffs == nil {
+		coeffs, err := prs.computeCoefficients()
+		if err != nil {
+			panic(err)
+		}
+		prs.coeffs = coeffs
+	}
+	endIndex := prs.GetEndIndex()
+	x, y = prs.InnerSeries.GetValues(endIndex)
+	y = prs.apply(x)
+	return
+}
+
+func (prs *PolynomialRegressionSeries) apply(v float64) (out float64) {
+	for index, coeff := range prs.coeffs {
+		out = out + (coeff * math.Pow(v, float64(index)))
+	}
+	return
+}
+
+func (prs *PolynomialRegressionSeries) computeCoefficients() ([]float64, error) {
+	xvalues, yvalues := prs.values()
+	return matrix.Poly(xvalues, yvalues, prs.Degree)
+}
+
+func (prs *PolynomialRegressionSeries) values() (xvalues, yvalues []float64) {
+	startIndex := prs.GetOffset()
+	endIndex := prs.GetEndIndex()
+
+	xvalues = make([]float64, endIndex-startIndex)
+	yvalues = make([]float64, endIndex-startIndex)
+
+	for index := startIndex; index < endIndex; index++ {
+		x, y := prs.InnerSeries.GetValues(index)
+		xvalues[index-startIndex] = x
+		yvalues[index-startIndex] = y
+	}
+
+	return
+}
+
+// Render renders the series.
+func (prs *PolynomialRegressionSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
+	style := prs.Style.InheritFrom(defaults)
+	Draw.LineSeries(r, canvasBox, xrange, yrange, style, prs)
+}