tests.

examples/linear_regression/main.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"net/http"
+
+	"github.com/wcharczuk/go-chart"
+)
+
+func drawChart(res http.ResponseWriter, req *http.Request) {
+
+	/*
+		In this example we add a new type of series, a `SimpleMovingAverageSeries` that takes another series as a required argument.
+		InnerSeries only needs to implement `ValueProvider`, so really you could chain `SimpleMovingAverageSeries` together if you wanted.
+	*/
+
+	mainSeries := chart.ContinuousSeries{
+		Name:    "A test series",
+		XValues: chart.Seq(1.0, 100.0),   //generates a []float64 from 1.0 to 100.0 in 1.0 step increments, or 100 elements.
+		YValues: chart.SeqRand(100, 100), //generates a []float64 randomly from 0 to 100 with 100 elements.
+	}
+
+	// note we create a LinearRegressionSeries series by assignin the inner series.
+	// we need to use a reference because `.Render()` needs to modify state within the series.
+	linRegSeries := &chart.LinearRegressionSeries{
+		InnerSeries: mainSeries,
+	} // we can optionally set the `WindowSize` property which alters how the moving average is calculated.
+
+	graph := chart.Chart{
+		Series: []chart.Series{
+			mainSeries,
+			linRegSeries,
+		},
+	}
+
+	res.Header().Set("Content-Type", "image/png")
+	graph.Render(chart.PNG, res)
+}
+
+func main() {
+	http.HandleFunc("/", drawChart)
+	http.ListenAndServe(":8080", nil)
+}

linear_regression_series.go

@@ -0,0 +1,135 @@
+package chart
+
+// LinearRegressionSeries is a series that plots the n-nearest neighbors
+// linear regression for the values.
+type LinearRegressionSeries struct {
+	Name  string
+	Style Style
+	YAxis YAxisType
+
+	Window      int
+	Offset      int
+	InnerSeries ValueProvider
+
+	m       float64
+	b       float64
+	avgx    float64
+	stddevx float64
+}
+
+// GetName returns the name of the time series.
+func (lrs LinearRegressionSeries) GetName() string {
+	return lrs.Name
+}
+
+// GetStyle returns the line style.
+func (lrs LinearRegressionSeries) GetStyle() Style {
+	return lrs.Style
+}
+
+// GetYAxis returns which YAxis the series draws on.
+func (lrs LinearRegressionSeries) GetYAxis() YAxisType {
+	return lrs.YAxis
+}
+
+// Len returns the number of elements in the series.
+func (lrs LinearRegressionSeries) Len() int {
+	return lrs.InnerSeries.Len()
+}
+
+// GetWindow returns the window size.
+func (lrs LinearRegressionSeries) GetWindow() int {
+	if lrs.Window == 0 {
+		return lrs.InnerSeries.Len()
+	}
+	return lrs.Window
+}
+
+// GetEffectiveWindowEnd returns the effective window end.
+func (lrs LinearRegressionSeries) GetEffectiveWindowEnd() int {
+	offset := lrs.GetOffset()
+	windowEnd := offset + lrs.GetWindow()
+	return MinInt(windowEnd, lrs.Len()-1)
+}
+
+// GetOffset returns the data offset.
+func (lrs LinearRegressionSeries) GetOffset() int {
+	if lrs.Offset == 0 {
+		return 0
+	}
+	return lrs.Offset
+}
+
+// GetValue gets a value at a given index.
+func (lrs *LinearRegressionSeries) GetValue(index int) (x, y float64) {
+	if lrs.InnerSeries == nil {
+		return
+	}
+	if lrs.m == 0 && lrs.b == 0 {
+		lrs.computeCoefficients()
+	}
+	offset := lrs.GetOffset()
+	x, y = lrs.InnerSeries.GetValue(index + offset)
+	y = (lrs.m * lrs.normalize(x)) + lrs.b
+	return
+}
+
+// GetLastValue computes the last moving average value but walking back window size samples,
+// and recomputing the last moving average chunk.
+func (lrs *LinearRegressionSeries) GetLastValue() (x, y float64) {
+	if lrs.InnerSeries == nil {
+		return
+	}
+	if lrs.m == 0 && lrs.b == 0 {
+		lrs.computeCoefficients()
+	}
+	endIndex := lrs.GetEffectiveWindowEnd()
+	x, y = lrs.InnerSeries.GetValue(endIndex)
+	y = (lrs.m * lrs.normalize(x)) + lrs.b
+	return
+}
+
+func (lrs *LinearRegressionSeries) normalize(xvalue float64) float64 {
+	return (xvalue - lrs.avgx) / lrs.stddevx
+}
+
+// computeCoefficients computes the `m` and `b` terms in the linear formula given by `y = mx+b`.
+func (lrs *LinearRegressionSeries) computeCoefficients() {
+
+	startIndex := lrs.GetOffset()
+	endIndex := lrs.GetEffectiveWindowEnd()
+
+	valueCount := endIndex - startIndex
+
+	p := float64(endIndex - startIndex)
+
+	xvalues := NewRingBufferWithCapacity(valueCount)
+	for index := startIndex; index < endIndex; index++ {
+		x, _ := lrs.InnerSeries.GetValue(index)
+		xvalues.Enqueue(x)
+	}
+
+	lrs.avgx = xvalues.Average()
+	lrs.stddevx = xvalues.StdDev()
+
+	var sumx, sumy, sumxx, sumxy float64
+	for index := startIndex; index < endIndex; index++ {
+		x, y := lrs.InnerSeries.GetValue(index)
+
+		x = lrs.normalize(x)
+
+		sumx += x
+		sumy += y
+		sumxx += x * x
+		sumxy += x * y
+	}
+
+	lrs.m = (p*sumxy - sumx*sumy) / (p*sumxx - sumx*sumx)
+	lrs.b = (sumy / p) - (lrs.m * sumx / p)
+}
+
+// Render renders the series.
+func (lrs *LinearRegressionSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
+	style := lrs.Style.InheritFrom(defaults)
+	DrawLineSeries(r, canvasBox, xrange, yrange, style, lrs)
+}

linear_regression_series_test.go

@@ -0,0 +1,75 @@
+package chart
+
+import (
+	"testing"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestLinearRegressionSeries(t *testing.T) {
+	assert := assert.New(t)
+
+	mainSeries := ContinuousSeries{
+		Name:    "A test series",
+		XValues: Seq(1.0, 100.0),
+		YValues: Seq(1.0, 100.0),
+	}
+
+	linRegSeries := &LinearRegressionSeries{
+		InnerSeries: mainSeries,
+	}
+
+	lrx0, lry0 := linRegSeries.GetValue(0)
+	assert.InDelta(1.0, lrx0, 0.0000001)
+	assert.InDelta(1.0, lry0, 0.0000001)
+
+	lrxn, lryn := linRegSeries.GetLastValue()
+	assert.InDelta(100.0, lrxn, 0.0000001)
+	assert.InDelta(100.0, lryn, 0.0000001)
+}
+
+func TestLinearRegressionSeriesDesc(t *testing.T) {
+	assert := assert.New(t)
+
+	mainSeries := ContinuousSeries{
+		Name:    "A test series",
+		XValues: Seq(100.0, 1.0),
+		YValues: Seq(100.0, 1.0),
+	}
+
+	linRegSeries := &LinearRegressionSeries{
+		InnerSeries: mainSeries,
+	}
+
+	lrx0, lry0 := linRegSeries.GetValue(0)
+	assert.InDelta(100.0, lrx0, 0.0000001)
+	assert.InDelta(100.0, lry0, 0.0000001)
+
+	lrxn, lryn := linRegSeries.GetLastValue()
+	assert.InDelta(1.0, lrxn, 0.0000001)
+	assert.InDelta(1.0, lryn, 0.0000001)
+}
+
+func TestLinearRegressionSeriesWindowAndOffset(t *testing.T) {
+	assert := assert.New(t)
+
+	mainSeries := ContinuousSeries{
+		Name:    "A test series",
+		XValues: Seq(100.0, 1.0),
+		YValues: Seq(100.0, 1.0),
+	}
+
+	linRegSeries := &LinearRegressionSeries{
+		InnerSeries: mainSeries,
+		Offset:      10,
+		Window:      10,
+	}
+
+	lrx0, lry0 := linRegSeries.GetValue(0)
+	assert.InDelta(90.0, lrx0, 0.0000001)
+	assert.InDelta(90.0, lry0, 0.0000001)
+
+	lrxn, lryn := linRegSeries.GetLastValue()
+	assert.InDelta(80.0, lrxn, 0.0000001)
+	assert.InDelta(80.0, lryn, 0.0000001)
+}

market_hours_range_test.go

@@ -55,7 +55,7 @@ func TestMarketHoursRangeGetTicks(t *testing.T) {
 
 	ticks := r.GetTicks(TimeValueFormatter)
 	assert.NotEmpty(ticks)
-	assert.Len(ticks, 5)
+	assert.Len(ticks, 6)
 	assert.NotEqual(TimeToFloat64(r.Min), ticks[0].Value)
 	assert.NotEmpty(ticks[0].Label)
 }

ring_buffer.go

@@ -2,6 +2,7 @@ package chart
 
 import (
 	"fmt"
+	"math"
 	"strings"
 )
 
@@ -200,6 +201,40 @@ func (rb *RingBuffer) String() string {
 	return strings.Join(values, " <= ")
 }
 
+// Average returns the float average of the values in the buffer.
+func (rb *RingBuffer) Average() float64 {
+	var accum float64
+	rb.Each(func(v interface{}) {
+		if typed, isTyped := v.(float64); isTyped {
+			accum += typed
+		}
+	})
+	return accum / float64(rb.Len())
+}
+
+// Variance computes the variance of the buffer.
+func (rb *RingBuffer) Variance() float64 {
+	if rb.Len() == 0 {
+		return 0
+	}
+
+	var variance float64
+	m := rb.Average()
+
+	rb.Each(func(v interface{}) {
+		if n, isTyped := v.(float64); isTyped {
+			variance += (float64(n) - m) * (float64(n) - m)
+		}
+	})
+
+	return variance / float64(rb.Len())
+}
+
+// StdDev returns the standard deviation.
+func (rb *RingBuffer) StdDev() float64 {
+	return math.Pow(rb.Variance(), 0.5)
+}
+
 func arrayClear(source []interface{}, index, length int) {
 	for x := 0; x < length; x++ {
 		absoluteIndex := x + index

sma_series.go

@@ -35,6 +35,17 @@ func (sma SMASeries) Len() int {
 	return sma.InnerSeries.Len()
 }
 
+// GetPeriod returns the window size.
+func (sma SMASeries) GetPeriod(defaults ...int) int {
+	if sma.Period == 0 {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+		return DefaultSimpleMovingAveragePeriod
+	}
+	return sma.Period
+}
+
 // GetValue gets a value at a given index.
 func (sma SMASeries) GetValue(index int) (x, y float64) {
 	if sma.InnerSeries == nil {
@@ -59,17 +70,6 @@ func (sma SMASeries) GetLastValue() (x, y float64) {
 	return
 }
 
-// GetPeriod returns the window size.
-func (sma SMASeries) GetPeriod(defaults ...int) int {
-	if sma.Period == 0 {
-		if len(defaults) > 0 {
-			return defaults[0]
-		}
-		return DefaultSimpleMovingAveragePeriod
-	}
-	return sma.Period
-}
-
 func (sma SMASeries) getAverage(index int) float64 {
 	period := sma.GetPeriod()
 	floor := MaxInt(0, index-period)

xaxis.go

@@ -28,8 +28,11 @@ func (xa XAxis) GetStyle() Style {
 	return xa.Style
 }
 
-// GetTicks returns the ticks for a series. It coalesces between user provided ticks and
+// GetTicks returns the ticks for a series.
-// generated ticks.
+// The coalesce priority is:
+// 	- User Supplied Ticks (i.e. Ticks array on the axis itself).
+// 	- Range ticks (i.e. if the range provides ticks).
+//	- Generating continuous ticks based on minimum spacing and canvas width.
 func (xa XAxis) GetTicks(r Renderer, ra Range, defaults Style, vf ValueFormatter) []Tick {
 	if len(xa.Ticks) > 0 {
 		return xa.Ticks

yaxis.go

@@ -35,8 +35,11 @@ func (ya YAxis) GetStyle() Style {
 	return ya.Style
 }
 
-// GetTicks returns the ticks for a series. It coalesces between user provided ticks and
+// GetTicks returns the ticks for a series.
-// generated ticks.
+// The coalesce priority is:
+// 	- User Supplied Ticks (i.e. Ticks array on the axis itself).
+// 	- Range ticks (i.e. if the range provides ticks).
+//	- Generating continuous ticks based on minimum spacing and canvas width.
 func (ya YAxis) GetTicks(r Renderer, ra Range, defaults Style, vf ValueFormatter) []Tick {
 	if len(ya.Ticks) > 0 {
 		return ya.Ticks