package indicator import ( "github.com/c9s/bbgo/pkg/types" ) // Refer: Double Exponential Moving Average // Refer URL: https://investopedia.com/terms/d/double-exponential-moving-average.asp //go:generate callbackgen -type DEMA type DEMA struct { types.IntervalWindow types.SeriesBase Values types.Float64Slice a1 *EWMA a2 *EWMA UpdateCallbacks []func(value float64) } func (inc *DEMA) Update(value float64) { if len(inc.Values) == 0 { inc.SeriesBase.Series = inc inc.a1 = &EWMA{IntervalWindow: types.IntervalWindow{inc.Interval, inc.Window}} inc.a2 = &EWMA{IntervalWindow: types.IntervalWindow{inc.Interval, inc.Window}} } inc.a1.Update(value) inc.a2.Update(inc.a1.Last()) inc.Values.Push(2*inc.a1.Last() - inc.a2.Last()) if len(inc.Values) > MaxNumOfEWMA { inc.Values = inc.Values[MaxNumOfEWMATruncateSize-1:] } } func (inc *DEMA) Last() float64 { return inc.Values.Last() } func (inc *DEMA) Index(i int) float64 { if len(inc.Values)-i-1 >= 0 { return inc.Values[len(inc.Values)-1-i] } return 0 } func (inc *DEMA) Length() int { return len(inc.Values) } var _ types.SeriesExtend = &DEMA{} func (inc *DEMA) calculateAndUpdate(allKLines []types.KLine) { if inc.a1 == nil { for _, k := range allKLines { inc.Update(k.Close.Float64()) inc.EmitUpdate(inc.Last()) } } else { inc.Update(allKLines[len(allKLines)-1].Close.Float64()) inc.EmitUpdate(inc.Last()) } } func (inc *DEMA) handleKLineWindowUpdate(interval types.Interval, window types.KLineWindow) { if inc.Interval != interval { return } inc.calculateAndUpdate(window) } func (inc *DEMA) Bind(updater KLineWindowUpdater) { updater.OnKLineWindowUpdate(inc.handleKLineWindowUpdate) }