feat(validation): add input validation for Bilateral and Blma constructors; enhance Butter and Mgdi calculations with NaN handling

lib/trends/jma/Jma.Tests.cs

@@ -237,6 +237,25 @@ public class JmaTests
         Assert.NotEqual(jmaPhase0.Last.Value, jmaPhaseMinus100.Last.Value);
     }
 
+    [Fact]
+    public void Jma_Power_AffectsResult()
+    {
+        var series = new TSeries();
+        var gbm = new GBM(startPrice: 100.0, mu: 0.02, sigma: 0.1, seed: 42);
+        for (int i = 0; i < 100; i++)
+        {
+            var bar = gbm.Next(isNew: true);
+            series.Add(bar.Time, bar.Close);
+        }
+
+        var jmaPowerDefault = Jma.Batch(series, 10, power: 0.45);
+        var jmaPower1 = Jma.Batch(series, 10, power: 1.0);
+        var jmaPower2 = Jma.Batch(series, 10, power: 2.0);
+
+        Assert.NotEqual(jmaPowerDefault.Last.Value, jmaPower1.Last.Value);
+        Assert.NotEqual(jmaPowerDefault.Last.Value, jmaPower2.Last.Value);
+    }
+
 
     [Fact]
     public void Jma_SpanCalc_HandlesNaN()

lib/trends/jma/Jma.cs

@@ -24,6 +24,7 @@ public sealed class Jma : AbstractBase
     private readonly double _lengthDivider;  // L'/(L'+2), L' = 0.9*L
     private readonly double _logSqrtDivider; // Precomputed log(_sqrtDivider) for Exp optimization
     private readonly double _logLengthDivider; // Precomputed log(_lengthDivider) for Exp optimization
+    private readonly double _power;          // Jurik power parameter
 
     // Constants for trimmed mean
     private const int JurikTrimCount = 65; // canonical JMA: middle 65 of 128 samples
@@ -71,6 +72,8 @@ public sealed class Jma : AbstractBase
         else
             _phaseParam = (phase * 0.01) + 1.5;
 
+        _power = power;
+
         // --- Length / log / divider parameters (from decompiled JMA) ---
         // L_raw ~ (period - 1)/2, with a tiny lower bound to avoid log(0)
         double lengthParam = period < 1.0000000002
@@ -144,7 +147,11 @@ public sealed class Jma : AbstractBase
         // --- Handle NaN/inf: reuse last finite price ---
         if (!double.IsFinite(value))
         {
-            value = _state.Bars > 0 ? _state.LastPrice : 0.0;
+            if (_state.Bars == 0)
+            {
+                return double.NaN;
+            }
+            value = _state.LastPrice;
         }
         else
         {
@@ -189,8 +196,7 @@ public sealed class Jma : AbstractBase
         double ratio = absValue / refVolatility;
         if (ratio < 0.0) ratio = 0.0;
 
-        double p = Math.Max(_logParam - 2.0, 0.5);
-        double d = Math.Pow(ratio, p);
+        double d = Math.Pow(ratio, _power);
         if (d > _logParam) d = _logParam;
         if (d < 1.0) d = 1.0;