last annotation helper

examples/min_max/main.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"net/http"
+
+	"github.com/wcharczuk/go-chart"
+)
+
+func drawChart(res http.ResponseWriter, req *http.Request) {
+	mainSeries := chart.ContinuousSeries{
+		Name:    "A test series",
+		XValues: chart.Sequence.Float64(1.0, 100.0),
+		YValues: chart.Sequence.RandomWithAverage(100, 100, 50),
+	}
+
+	minSeries := &chart.MinSeries{
+		Style: chart.Style{
+			Show:            true,
+			StrokeColor:     chart.ColorAlternateGray,
+			StrokeDashArray: []float64{5.0, 5.0},
+		},
+		InnerSeries: mainSeries,
+	}
+
+	maxSeries := &chart.MaxSeries{
+		Style: chart.Style{
+			Show:            true,
+			StrokeColor:     chart.ColorAlternateGray,
+			StrokeDashArray: []float64{5.0, 5.0},
+		},
+		InnerSeries: mainSeries,
+	}
+
+	graph := chart.Chart{
+		YAxis: chart.YAxis{
+			Style: chart.StyleShow(),
+			Range: &chart.ContinuousRange{
+				Min: 25,
+				Max: 175,
+			},
+		},
+		XAxis: chart.XAxis{
+			Style: chart.StyleShow(),
+		},
+		Series: []chart.Series{
+			mainSeries,
+			minSeries,
+			maxSeries,
+			chart.LastValueAnnotation(minSeries),
+			chart.LastValueAnnotation(maxSeries),
+		},
+	}
+
+	res.Header().Set("Content-Type", "image/png")
+	graph.Render(chart.PNG, res)
+}
+
+func main() {
+	http.HandleFunc("/", drawChart)
+	http.ListenAndServe(":8080", nil)
+}

last_value_annotation_series.go

@@ -0,0 +1,37 @@
+package chart
+
+import "fmt"
+
+// LastValueAnnotation returns an annotation series of just the last value of a value provider.
+func LastValueAnnotation(innerSeries ValueProvider, vfs ...ValueFormatter) AnnotationSeries {
+	var vf ValueFormatter
+	if len(vfs) > 0 {
+		vf = vfs[0]
+	} else if typed, isTyped := innerSeries.(ValueFormatterProvider); isTyped {
+		_, vf = typed.GetValueFormatters()
+	} else {
+		vf = FloatValueFormatter
+	}
+
+	var lastValue Value2
+	if typed, isTyped := innerSeries.(LastValueProvider); isTyped {
+		lastValue.XValue, lastValue.YValue = typed.GetLastValue()
+		lastValue.Label = vf(lastValue.YValue)
+	} else {
+		lastValue.XValue, lastValue.YValue = innerSeries.GetValue(innerSeries.Len() - 1)
+		lastValue.Label = vf(lastValue.YValue)
+	}
+
+	var seriesName string
+	var seriesStyle Style
+	if typed, isTyped := innerSeries.(Series); isTyped {
+		seriesName = fmt.Sprintf("%s - Last Value", typed.GetName())
+		seriesStyle = typed.GetStyle()
+	}
+
+	return AnnotationSeries{
+		Name:        seriesName,
+		Style:       seriesStyle,
+		Annotations: []Value2{lastValue},
+	}
+}

min_max_series.go

@@ -0,0 +1,119 @@
+package chart
+
+import "math"
+
+// MinSeries draws a horizontal line at the minimum value of the inner series.
+type MinSeries struct {
+	Name        string
+	Style       Style
+	YAxis       YAxisType
+	InnerSeries ValueProvider
+
+	minValue *float64
+}
+
+// GetName returns the name of the time series.
+func (ms MinSeries) GetName() string {
+	return ms.Name
+}
+
+// GetStyle returns the line style.
+func (ms MinSeries) GetStyle() Style {
+	return ms.Style
+}
+
+// GetYAxis returns which YAxis the series draws on.
+func (ms MinSeries) GetYAxis() YAxisType {
+	return ms.YAxis
+}
+
+// Len returns the number of elements in the series.
+func (ms MinSeries) Len() int {
+	return ms.InnerSeries.Len()
+}
+
+// GetValue gets a value at a given index.
+func (ms *MinSeries) GetValue(index int) (x, y float64) {
+	ms.ensureMinValue()
+	x, _ = ms.InnerSeries.GetValue(index)
+	y = *ms.minValue
+	return
+}
+
+// Render renders the series.
+func (ms *MinSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
+	style := ms.Style.InheritFrom(defaults)
+	Draw.LineSeries(r, canvasBox, xrange, yrange, style, ms)
+}
+
+func (ms *MinSeries) ensureMinValue() {
+	if ms.minValue == nil {
+		minValue := math.MaxFloat64
+		var y float64
+		for x := 0; x < ms.InnerSeries.Len(); x++ {
+			_, y = ms.InnerSeries.GetValue(x)
+			if y < minValue {
+				minValue = y
+			}
+		}
+		ms.minValue = &minValue
+	}
+}
+
+// MaxSeries draws a horizontal line at the maximum value of the inner series.
+type MaxSeries struct {
+	Name        string
+	Style       Style
+	YAxis       YAxisType
+	InnerSeries ValueProvider
+
+	maxValue *float64
+}
+
+// GetName returns the name of the time series.
+func (ms MaxSeries) GetName() string {
+	return ms.Name
+}
+
+// GetStyle returns the line style.
+func (ms MaxSeries) GetStyle() Style {
+	return ms.Style
+}
+
+// GetYAxis returns which YAxis the series draws on.
+func (ms MaxSeries) GetYAxis() YAxisType {
+	return ms.YAxis
+}
+
+// Len returns the number of elements in the series.
+func (ms MaxSeries) Len() int {
+	return ms.InnerSeries.Len()
+}
+
+// GetValue gets a value at a given index.
+func (ms *MaxSeries) GetValue(index int) (x, y float64) {
+	ms.ensureMaxValue()
+	x, _ = ms.InnerSeries.GetValue(index)
+	y = *ms.maxValue
+	return
+}
+
+// Render renders the series.
+func (ms *MaxSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
+	style := ms.Style.InheritFrom(defaults)
+	Draw.LineSeries(r, canvasBox, xrange, yrange, style, ms)
+}
+
+func (ms *MaxSeries) ensureMaxValue() {
+	if ms.maxValue == nil {
+		maxValue := -math.MaxFloat64
+		var y float64
+		for x := 0; x < ms.InnerSeries.Len(); x++ {
+			_, y = ms.InnerSeries.GetValue(x)
+			if y > maxValue {
+				maxValue = y
+			}
+		}
+		ms.maxValue = &maxValue
+	}
+}