From 3d413e84514d12c1681ea8782cb43fe81fa93b2e Mon Sep 17 00:00:00 2001
From: Dave Skender <8432125+DaveSkender@users.noreply.github.com>
Date: Sat, 4 Nov 2023 04:18:54 -0400
Subject: [PATCH] fix #1107

---
 src/s-z/Stoch/Stoch.Series.cs         |  4 ++--
 tests/indicators/s-z/Stc/Stc.Tests.cs | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/s-z/Stoch/Stoch.Series.cs b/src/s-z/Stoch/Stoch.Series.cs
index debcb40b4..3f0aaa22e 100644
--- a/src/s-z/Stoch/Stoch.Series.cs
+++ b/src/s-z/Stoch/Stoch.Series.cs
@@ -73,7 +73,7 @@ internal static List<StochResult> CalcStoch(
 
         // signal (%D) and %J
         int signalIndex = lookbackPeriods + smoothPeriods + signalPeriods - 2;
-        double? s = results[lookbackPeriods - 1].Oscillator;
+        double? s = null;
 
         for (int i = lookbackPeriods - 1; i < length; i++)
         {
@@ -102,7 +102,7 @@ internal static List<StochResult> CalcStoch(
             // SMMA case
             else if (i >= lookbackPeriods - 1 && movingAverageType is MaType.SMMA)
             {
-                s ??= results[i].Oscillator; // reset if null
+                s ??= results[i].Oscillator; // set initial or reset if null
 
                 s = ((s * (signalPeriods - 1)) + results[i].Oscillator) / signalPeriods;
                 r.Signal = s;
diff --git a/tests/indicators/s-z/Stc/Stc.Tests.cs b/tests/indicators/s-z/Stc/Stc.Tests.cs
index 80c73566e..23f9066fb 100644
--- a/tests/indicators/s-z/Stc/Stc.Tests.cs
+++ b/tests/indicators/s-z/Stc/Stc.Tests.cs
@@ -118,6 +118,20 @@ public void NoQuotes()
         Assert.AreEqual(1, r1.Count);
     }
 
+    [TestMethod]
+    public void Issue1107()
+    {
+        // stochastic SMMA variant initialization bug
+
+        RandomGbm quotes = new(58);
+
+        List<StcResult> results = quotes
+            .GetStc(10, 23, 50)
+            .ToList();
+
+        Assert.AreEqual(58, results.Count);
+    }
+
     [TestMethod]
     public void Removed()
     {