adding a GetLastValue() function to MovingAverageSeries.

moving_average_series.go

@@ -39,6 +39,9 @@ func (mas *MovingAverageSeries) Len() int {
 
 // GetValue gets a value at a given index.
 func (mas *MovingAverageSeries) GetValue(index int) (x float64, y float64) {
+	if mas.InnerSeries == nil {
+		return
+	}
 	if mas.valueBuffer == nil {
 		mas.valueBuffer = NewRingBufferWithCapacity(mas.GetWindowSize())
 	}
@@ -48,7 +51,29 @@ func (mas *MovingAverageSeries) GetValue(index int) (x float64, y float64) {
 	px, py := mas.InnerSeries.GetValue(index)
 	mas.valueBuffer.Enqueue(py)
 	x = px
-	y = mas.getAverage()
+	y = mas.getAverage(mas.valueBuffer)
+	return
+}
+
+// GetLastValue computes the last moving average value but walking back window size samples,
+// and recomputing the last moving average chunk.
+func (mas MovingAverageSeries) GetLastValue() (x float64, y float64) {
+	if mas.InnerSeries == nil {
+		return
+	}
+	windowSize := mas.GetWindowSize()
+	seriesLength := mas.InnerSeries.Len()
+	startAt := seriesLength - (windowSize + 1)
+	if (seriesLength - startAt) < 0 {
+		startAt = 0
+	}
+	vb := NewRingBufferWithCapacity(windowSize)
+	for index := startAt; index < seriesLength; index++ {
+		xn, yn := mas.InnerSeries.GetValue(index)
+		vb.Enqueue(yn)
+		x = xn
+	}
+	y = mas.getAverage(vb)
 	return
 }
 
@@ -63,9 +88,9 @@ func (mas MovingAverageSeries) GetWindowSize(defaults ...int) int {
 	return mas.WindowSize
 }
 
-func (mas MovingAverageSeries) getAverage() float64 {
+func (mas MovingAverageSeries) getAverage(valueBuffer *RingBuffer) float64 {
 	var accum float64
-	mas.valueBuffer.Each(func(v interface{}) {
+	valueBuffer.Each(func(v interface{}) {
 		if typed, isTyped := v.(float64); isTyped {
 			accum += typed
 		}