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指标(Indicator)由三大关键组件组成:
1. 实现你指标的类
2. 在ACAlgorithm基类中的Helper方法,用于简化对你指标实现的调用。
3. 测试方法用于测试指标的表现。
为了实现一个指标,上述所有组件需要实现。下面的教程会带你浏览这些组件。我们将会使用 AroonOscillator作为案例。我们不会去介绍指标的基本概念。
1. 实现你的指标(Implementing Your Indicator)
你的指标类应该在工程根下的QuantConnect.Indicators项目下实现。它必须是一个单独的类,不能缩写,名如“AroonOscillator.cs”。
第一步
指标必须是下面指标基类的一个派生:
Indicator – 如果你的指标只需要单个值(例如ExponontialMovingAverage),你就可以用Indicator作为基类。
TradeBarIndicator – 如果你的指标需要用到TradeBars,那么你的指标必须是由TradeBarIndicator类扩展而来的。(例如AroonOscillator)。
WindowIndicator<T> - 如果你的指标需要一个rolling window of data(数据的滚动窗口),那么你就要继承这个类。(例如Minimum)。
所有的指标都必须实现下面四个组件,为了在Lean中正常运作。
Constructor – 实现你的构造函数,用于接收和保存必要的指标配置信息。例如Aroon指标需要Aroon Up 和 Aroon Down值。
IsReady – 它是一个Boolean值,用于指示算法是否有了充足的历史价格数据用于算出指标的值。Aroon只有当有了n个周期的样本数据后才能开始计算。
ComputeNextValue()- 用提供的数据,计算和返回下一个指标的值。这里是你实现指标具体算法的地方。
保持可扩展性
Aroon作为案例是非常有代表性的,它有多个属性,Aroon-Up和Aroon-Down。这两个值在计算Aroon的时候都需要用到,但只有delta(up – down)会返回。这个例子中的dela叫做Aroon Percentage(比例)。许多指标会有一个主值(Primary value),多个属性,用于交易决策。
为了处理这些情况-每个属性都应该作为子指标(sub-indicator)。你可以查看下AroonOscillator.cs的源码。Aroon创建了AroonUp,AroonDown指标作为属性。这使得你可以单独的使用这些子指标。
例如下面的代码:
var smaAroonUp = sma.Of( aroon.AroonUp )
就直接用属性(子指标)。
现在我们贴出AroonOscillator的代码:
using QuantConnect.Data.Market; namespace QuantConnect.Indicators { /// <summary> /// The Aroon Oscillator is the difference between AroonUp and AroonDown. The value of this /// indicator fluctuats between -100 and +100. An upward trend bias is present when the oscillator /// is positive, and a negative trend bias is present when the oscillator is negative. AroonUp/Down /// values over 75 identify strong trends in their respective direction. /// </summary> public class AroonOscillator : TradeBarIndicator { /// <summary> /// Gets the AroonUp indicator /// </summary> public IndicatorBase<IndicatorDataPoint> AroonUp { get; private set; } /// <summary> /// Gets the AroonDown indicator /// </summary> public IndicatorBase<IndicatorDataPoint> AroonDown { get; private set; } /// <summary> /// Gets a flag indicating when this indicator is ready and fully initialized /// </summary> public override bool IsReady { get { return AroonUp.IsReady && AroonDown.IsReady; } } /// <summary> /// Creates a new AroonOscillator from the specified up/down periods. /// </summary> /// <param name="upPeriod">The lookback period to determine the highest high for the AroonDown</param> /// <param name="downPeriod">The lookback period to determine the lowest low for the AroonUp</param> public AroonOscillator(int upPeriod, int downPeriod) : this(string.Format("AROON({0},{1})", upPeriod, downPeriod), upPeriod, downPeriod) { } /// <summary> /// Creates a new AroonOscillator from the specified up/down periods. /// </summary> /// <param name="name">The name of this indicator</param> /// <param name="upPeriod">The lookback period to determine the highest high for the AroonDown</param> /// <param name="downPeriod">The lookback period to determine the lowest low for the AroonUp</param> public AroonOscillator(string name, int upPeriod, int downPeriod) : base(name) { var max = new Maximum(name + "_Max", upPeriod + 1); AroonUp = new FunctionalIndicator<IndicatorDataPoint>(name + "_AroonUp", input => ComputeAroonUp(upPeriod, max, input), aroonUp => max.IsReady, () => max.Reset() ); var min = new Minimum(name + "_Min", downPeriod + 1); AroonDown = new FunctionalIndicator<IndicatorDataPoint>(name + "_AroonDown", input => ComputeAroonDown(downPeriod, min, input), aroonDown => min.IsReady, () => min.Reset() ); } /// <summary> /// Computes the next value of this indicator from the given state /// </summary> /// <param name="input">The input given to the indicator</param> /// <returns>A new value for this indicator</returns> protected override decimal ComputeNextValue(TradeBar input) { AroonUp.Update(input.Time, input.High); AroonDown.Update(input.Time, input.Low); return AroonUp - AroonDown; } /// <summary> /// AroonUp = 100 * (period - {periods since max})/period /// </summary> /// <param name="upPeriod">The AroonUp period</param> /// <param name="max">A Maximum indicator used to compute periods since max</param> /// <param name="input">The next input data</param> /// <returns>The AroonUp value</returns> private static decimal ComputeAroonUp(int upPeriod, Maximum max, IndicatorDataPoint input) { max.Update(input); return 100m * (upPeriod - max.PeriodsSinceMaximum) / upPeriod; } /// <summary> /// AroonDown = 100 * (period - {periods since min})/period /// </summary> /// <param name="downPeriod">The AroonDown period</param> /// <param name="min">A Minimum indicator used to compute periods since min</param> /// <param name="input">The next input data</param> /// <returns>The AroonDown value</returns> private static decimal ComputeAroonDown(int downPeriod, Minimum min, IndicatorDataPoint input) { min.Update(input); return 100m * (downPeriod - min.PeriodsSinceMinimum) / downPeriod; } /// <summary> /// Resets this indicator and both sub-indicators (AroonUp and AroonDown) /// </summary> public override void Reset() { AroonUp.Reset(); AroonDown.Reset(); base.Reset(); } } }
2 在QCAlgorithm中安装Helper方法
在你实现了indicator(指标)之后,i需要将它安装到基类中。指标可以手工的创建和更新,不过我们加你使用helper方法,这样后面使用起来会简单很多。
在Aroon的案例中,实现是在AroonOscillator类,但它的helper方法是在QCAlgorithm中。这个helper方法—AROON—总是是大写的,总是返回一个指标实现类的实例对象。
public AroonOscillator AROON(string symbol, int upPeriod, int downPeriod, Resolution? resolution = null) { var name = CreateIndicatorName(symbol, string.Format("AROON({0},{1})", upPeriod, downPeriod), resolution); var aroon = new AroonOscillator(name, upPeriod, downPeriod); RegisterIndicator(symbol, aroon, resolution); return aroon; }
在helper方法中,你需要创建你指标的一个唯一的名字,使用你指标实现类的构造函数去构造一个指标实例,将其注册(注册后意味着指标的值会随着symbol(指定证券)的价格数据变动而自动的变动)。
3 创建测试方法
3.1 准备测试数据
将准备好的测试数据放到QuantConnect.Tests\TestData目录下。
3.2 写测试类
在QuantConnect.Tests\Indicators下面。可以拷贝已经有的进行改写。
using System; using NUnit.Framework; using QuantConnect.Data.Market; using QuantConnect.Indicators; namespace QuantConnect.Tests.Indicators { [TestFixture] public class AroonOscillatorTests { [Test] public void ComparesWithExternalData() { var aroon = new AroonOscillator(14, 14); TestHelper.TestIndicator(aroon, "spy_aroon_oscillator.txt", "Aroon Oscillator 14", (i, expected) => Assert.AreEqual(expected, (double)aroon.Current.Value, 1e-3)); } [Test] public void ResetsProperly() { var aroon = new AroonOscillator(3, 3); aroon.Update(new TradeBar { Symbol = "SPY", Time = DateTime.Today, Open = 3m, High = 7m, Low = 2m, Close = 5m, Volume = 10 }); aroon.Update(new TradeBar { Symbol = "SPY", Time = DateTime.Today.AddSeconds(1), Open = 3m, High = 7m, Low = 2m, Close = 5m, Volume = 10 }); aroon.Update(new TradeBar { Symbol = "SPY", Time = DateTime.Today.AddSeconds(2), Open = 3m, High = 7m, Low = 2m, Close = 5m, Volume = 10 }); Assert.IsFalse(aroon.IsReady); aroon.Update(new TradeBar { Symbol = "SPY", Time = DateTime.Today.AddSeconds(3), Open = 3m, High = 7m, Low = 2m, Close = 5m, Volume = 10 }); Assert.IsTrue(aroon.IsReady); aroon.Reset(); TestHelper.AssertIndicatorIsInDefaultState(aroon); TestHelper.AssertIndicatorIsInDefaultState(aroon.AroonUp); TestHelper.AssertIndicatorIsInDefaultState(aroon.AroonDown); } } }