Adding upstream version 2.1.2.

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

percent_change_series.go

@@ -0,0 +1,89 @@
+package chart
+
+// Interface Assertions.
+var (
+	_ Series                 = (*PercentChangeSeries)(nil)
+	_ FirstValuesProvider    = (*PercentChangeSeries)(nil)
+	_ LastValuesProvider     = (*PercentChangeSeries)(nil)
+	_ ValueFormatterProvider = (*PercentChangeSeries)(nil)
+)
+
+// PercentChangeSeriesSource is a series that
+// can be used with a PercentChangeSeries
+type PercentChangeSeriesSource interface {
+	Series
+	FirstValuesProvider
+	LastValuesProvider
+	ValuesProvider
+	ValueFormatterProvider
+}
+
+// PercentChangeSeries applies a
+// percentage difference function to a given continuous series.
+type PercentChangeSeries struct {
+	Name        string
+	Style       Style
+	YAxis       YAxisType
+	InnerSeries PercentChangeSeriesSource
+}
+
+// GetName returns the name of the time series.
+func (pcs PercentChangeSeries) GetName() string {
+	return pcs.Name
+}
+
+// GetStyle returns the line style.
+func (pcs PercentChangeSeries) GetStyle() Style {
+	return pcs.Style
+}
+
+// Len implements part of Series.
+func (pcs PercentChangeSeries) Len() int {
+	return pcs.InnerSeries.Len()
+}
+
+// GetFirstValues implements FirstValuesProvider.
+func (pcs PercentChangeSeries) GetFirstValues() (x, y float64) {
+	return pcs.InnerSeries.GetFirstValues()
+}
+
+// GetValues gets x, y values at a given index.
+func (pcs PercentChangeSeries) GetValues(index int) (x, y float64) {
+	_, fy := pcs.InnerSeries.GetFirstValues()
+	x0, y0 := pcs.InnerSeries.GetValues(index)
+	x = x0
+	y = PercentDifference(fy, y0)
+	return
+}
+
+// GetValueFormatters returns value formatter defaults for the series.
+func (pcs PercentChangeSeries) GetValueFormatters() (x, y ValueFormatter) {
+	x, _ = pcs.InnerSeries.GetValueFormatters()
+	y = PercentValueFormatter
+	return
+}
+
+// GetYAxis returns which YAxis the series draws on.
+func (pcs PercentChangeSeries) GetYAxis() YAxisType {
+	return pcs.YAxis
+}
+
+// GetLastValues gets the last values.
+func (pcs PercentChangeSeries) GetLastValues() (x, y float64) {
+	_, fy := pcs.InnerSeries.GetFirstValues()
+	x0, y0 := pcs.InnerSeries.GetLastValues()
+	x = x0
+	y = PercentDifference(fy, y0)
+	return
+}
+
+// Render renders the series.
+func (pcs PercentChangeSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
+	style := pcs.Style.InheritFrom(defaults)
+	Draw.LineSeries(r, canvasBox, xrange, yrange, style, pcs)
+}
+
+// Validate validates the series.
+func (pcs PercentChangeSeries) Validate() error {
+	return pcs.InnerSeries.Validate()
+}