docs: Add ADR custom indicator (example)

docs/examples/CustomIndicatorsLibrary/Adr.cs

@@ -0,0 +1,72 @@
+using System.Collections.ObjectModel;
+
+using Skender.Stock.Indicators;
+
+namespace Custom.Stock.Indicators;
+
+// Custom results classes
+// This inherits many of the extension methods, like .RemoveWarmupPeriods()
+public sealed class DrResult : ResultBase, IReusableResult
+{
+    // date property is inherited here,
+    // so you only need to add custom items
+    public decimal Dr { get; set; }
+
+    // to enable further chaining
+    double? IReusableResult.Value => (double)Dr;
+}
+
+public sealed class AdrResult : ResultBase, IReusableResult
+{
+    public decimal Dr { get; set; }
+    public double? Adr { get; set; }
+    public double? Adrp { get; set; }
+
+    double? IReusableResult.Value => Adrp;
+}
+
+public static partial class CustomIndicators
+{
+    // ADR calculation
+    public static IEnumerable<AdrResult> GetAdr<TQuote>(
+        this IEnumerable<TQuote> quotes,
+        int lookbackPeriods)
+        where TQuote : IQuote
+    {
+        // TODO: this a bit of a hack, only to demonstrate the concept
+        // of a custom indicator.  This may be added to the library in the future.
+
+        // sort quotes and convert to collection or list
+        Collection<TQuote> quotesList = quotes
+            .ToSortedCollection();
+
+        // initialize
+        int length = quotes.Count();
+
+        // daily range
+        List<DrResult> drResult = quotes
+            .Select(x => new DrResult
+            {
+                Date = x.Date,
+                Dr = x.High - x.Low
+            }).ToList();
+
+        // average daily range
+        List<AdrResult> results = drResult
+            .GetSma(lookbackPeriods)
+            .Select(x => new AdrResult
+            {
+                Date = x.Date,
+                Adr = x.Sma
+            }).ToList();
+
+        // combine, add average daily range percentage
+        for (int i = 0; i < length; i++)
+        {
+            results[i].Dr = drResult[i].Dr;
+            results[i].Adrp = results[i].Adr / (double)quotesList[i].Close;
+        }
+
+        return results;
+    }
+}

docs/examples/CustomIndicatorsLibrary/AtrWma.cs

@@ -15,7 +15,7 @@ public sealed class AtrWmaResult : ResultBase, IReusableResult
     double? IReusableResult.Value => AtrWma;
 }
 
-public static class CustomIndicators
+public static partial class CustomIndicators
 {
     // Custom ATR WMA calculation
     public static IEnumerable<AtrWmaResult> GetAtrWma<TQuote>(