refactor: move Decay/Edecay from trends_IIR to numerics; update filter signatures

- Move lib/trends_IIR/decay/ → lib/numerics/decay/
- Move lib/trends_IIR/edecay/ → lib/numerics/edecay/
- Update Category in Decay.md/Edecay.md from Trends (IIR) to Numerics
- Add DECAY/EDECAY entries to lib/numerics/_index.md and docs/indicators.md
- Update filter signature .md files and .svg assets
- Update trends_IIR signature docs (htit, mama, holt, etc.)
- All 163 tests passing, 0 warnings, 0 errors

docs/indicators.md

@@ -433,7 +433,9 @@ Mathematical transformations and derivative indicators. Building blocks for anal
 | [**WEIBULLDIST**](../lib/numerics/weibulldist/Weibulldist.md) | Weibull Distribution (CDF) | Rolling Weibull CDF — two-parameter closed-form probability transform via pow + exp |
 | [**CHANGE**](../lib/numerics/change/Change.md) | Percentage Change | Relative price movement |
 | [**CWT**](../lib/numerics/cwt/Cwt.md) | Continuous Wavelet Transform | Morlet CWT magnitude at a specified scale — time-frequency decomposition |
+| [**DECAY**](../lib/numerics/decay/Decay.md) | Linear Decay | Peak envelope with linear degradation |
 | [**DWT**](../lib/numerics/dwt/Dwt.md) | Discrete Wavelet Transform | À trous Haar stationary DWT — multi-resolution approximation + detail, WarmupPeriod = 2^levels |
+| [**EDECAY**](../lib/numerics/edecay/Edecay.md) | Exponential Decay | Peak envelope with exponential degradation |
 | [**EXPTRANS**](../lib/numerics/exptrans/Exptrans.md) | Exponential Transform | e^x for log-space reversal |
 | [**HIGHEST**](../lib/numerics/highest/Highest.md) | Rolling Maximum | O(1) via monotonic deque |
 | [**MAXINDEX**](../lib/numerics/maxindex/Maxindex.md) | Rolling Maximum Index | Position of max in window |

lib/filters/baxterking/BaxterKing.md

@@ -8,7 +8,6 @@
 | **Outputs**      | Single series (BaxterKing)                       |
 | **Output range** | Oscillates around zero           |
 | **Warmup**       | `2K+1` bars (default 25)         |
-| **Signature**    | [baxterking_signature](baxterking_signature.md) |
 
 ### TL;DR
 

lib/filters/baxterking/baxterking_signature.md

@@ -1,3 +0,0 @@
-# BAXTERKING Signature
-
-![BAXTERKING Signature](baxterking_signature.svg)

lib/filters/bpf/Bpf.md

@@ -8,7 +8,6 @@
 | **Outputs**      | Single series (BPF)                       |
 | **Output range** | Oscillates around zero           |
 | **Warmup**       | `Math.Max(lowerPeriod, upperPeriod)` bars                          |
-| **Signature**    | [bpf_signature](bpf_signature.md) |
 
 ### TL;DR
 

lib/filters/bpf/bpf_signature.md

@@ -1,3 +0,0 @@
-# BPF Signature
-
-![BPF Signature](bpf_signature.svg)

lib/filters/cfitz/Cfitz.md

@@ -8,7 +8,6 @@
 | **Outputs**      | Single series (Cfitz)                       |
 | **Output range** | Oscillates around zero           |
 | **Warmup**       | `2` bars                          |
-| **Signature**    | [cfitz_signature](cfitz_signature.md) |
 
 ### TL;DR
 

lib/filters/cfitz/cfitz_signature.md

@@ -1,3 +0,0 @@
-# CFITZ Signature
-
-![CFITZ Signature](cfitz_signature.svg)

lib/filters/gauss/Gauss.md

@@ -8,6 +8,8 @@
 | **Outputs**      | Single series (Gauss)                       |
 | **Output range** | Tracks input                     |
 | **Warmup**       | 1 bar                          |
+| **Signature**    | [gauss_signature](gauss_signature.md) |
+
 
 ### TL;DR
 

lib/filters/gauss/gauss_signature.md

@@ -0,0 +1,3 @@
+# ELLIPTIC Signature
+
+![GAUSS signature](gauss_signature.svg)

lib/filters/hp/Hp.md

@@ -8,6 +8,8 @@
 | **Outputs**      | Single series (HP)                       |
 | **Output range** | Tracks input                     |
 | **Warmup**       | 1 bar                          |
+| **Signature**    | [hp_signature](hp_signature.md) |
+
 
 ### TL;DR
 

lib/filters/hp/hp_signature.md

@@ -0,0 +1,3 @@
+# ELLIPTIC Signature
+
+![HP Signature](hp_signature.svg)

lib/filters/hpf/Hpf.md

@@ -8,7 +8,6 @@
 | **Outputs**      | Single series (HPF)                       |
 | **Output range** | Tracks input                     |
 | **Warmup**       | 1 bar                          |
-| **Signature**    | [hpf_signature](hpf_signature.md) |
 
 ### TL;DR
 

lib/filters/hpf/hpf_signature.md

@@ -1,3 +0,0 @@
-# HPF Signature
-
-![HPF Signature](hpf_signature.svg)

lib/filters/kalman/Kalman.md

@@ -8,6 +8,8 @@
 | **Outputs**      | Single series (Kalman)                       |
 | **Output range** | Tracks input                     |
 | **Warmup**       | `10` bars                          |
+| **Signature**    | [kalman_signature](kalman_signature.md) |
+
 
 ### TL;DR
 

lib/filters/kalman/kalman_signature.md

@@ -0,0 +1,3 @@
+# ELLIPTIC Signature
+
+![KALMAN Signature](kalman_signature.svg)

lib/filters/laguerre/Laguerre.md

@@ -8,6 +8,8 @@
 | **Outputs**      | Single series (Laguerre)                       |
 | **Output range** | Tracks input                     |
 | **Warmup**       | `WarmupBars` bars                          |
+| **Signature**    | [laguerre_signature](laguerre_signature.md) |
+
 
 ### TL;DR
 

lib/filters/laguerre/laguerre_signature.md

@@ -0,0 +1,3 @@
+# ELLIPTIC Signature
+
+![LAGUERRE Signature](laguerre_signature.svg)

lib/filters/oneeuro/OneEuro.md

@@ -8,6 +8,8 @@
 | **Outputs**      | Single series (OneEuro)                       |
 | **Output range** | Tracks input                     |
 | **Warmup**       | `1` bars                          |
+| **Signature**    | [oneeuro_signature](oneeuro_signature.md) |
+
 
 ### TL;DR
 

lib/filters/oneeuro/oneeuro_signature.md

@@ -0,0 +1,3 @@
+# LOESS Signature
+
+![ONEEURO Signature](oneeuro_signature.svg)

lib/filters/rls/Rls.md

@@ -8,6 +8,8 @@
 | **Outputs**      | Single series (RLS)                       |
 | **Output range** | Tracks input                     |
 | **Warmup**       | `order + 1` bars                          |
+| **Signature**    | [rls_signature](rls_signature.md) |
+
 
 ### TL;DR
 

lib/filters/rls/rls_signature.md

@@ -0,0 +1,3 @@
+# LOESS Signature
+
+![RLS Signature](rls_signature.svg)

lib/filters/voss/Voss.md

@@ -8,7 +8,6 @@
 | **Outputs**      | Single series (VOSS)                       |
 | **Output range** | Oscillates around zero           |
 | **Warmup**       | `period` bars                          |
-| **Signature**    | [voss_signature](voss_signature.md) |
 
 ### TL;DR
 

lib/filters/voss/voss_signature.md

@@ -1,3 +0,0 @@
-# VOSS Signature
-
-![VOSS Signature](voss_signature.svg)

lib/filters/wavelet/Wavelet.md

@@ -8,6 +8,8 @@
 | **Outputs**      | Single series (Wavelet)                       |
 | **Output range** | Tracks input                     |
 | **Warmup**       | `2^levels` bars (default 16)   |
+| **Signature**    | [wavelet_signature](wavelet_signature.md) |
+
 
 ### TL;DR
 

lib/filters/wavelet/wavelet_signature.md

@@ -0,0 +1,3 @@
+# SGF Signature
+
+![WAVELET Signature](wavelet_signature.svg)

lib/numerics/_index.md

@@ -10,8 +10,10 @@ Basic mathematical transforms and utility functions for time series. These build
 | [BETADIST](betadist/Betadist.md) | Beta Distribution | Beta probability distribution transform. |
 | [BINOMDIST](binomdist/Binomdist.md) | Binomial Distribution | Binomial probability distribution transform. |
 | [CHANGE](change/Change.md) | Percentage Change | Relative price movement over lookback period. |
+| [DECAY](decay/Decay.md) | Linear Decay | Peak envelope with linear degradation; max(input, prev − 1/period). |
 | [CWT](cwt/Cwt.md) | Continuous Wavelet Transform | Time-frequency decomposition with continuous wavelets. |
 | [DWT](dwt/Dwt.md) | Discrete Wavelet Transform | À trous Haar stationary DWT; multi-resolution approximation + detail decomposition. |
+| [EDECAY](edecay/Edecay.md) | Exponential Decay | Peak envelope with exponential degradation; max(input, prev × (period−1)/period). |
 | [EXPDIST](expdist/Expdist.md) | Exponential Distribution | Exponential probability distribution transform. |
 | [EXPTRANS](exptrans/Exptrans.md) | Exponential Transform | e^x transform for log-space conversion reversal. |
 | [FDIST](fdist/Fdist.md) | F-Distribution | Fisher-Snedecor probability distribution transform. |

lib/numerics/decay/Decay.md

@@ -2,7 +2,7 @@
 
 | Property         | Value                            |
 | ---------------- | -------------------------------- |
-| **Category**     | Trends (IIR)                     |
+| **Category**     | Numerics                         |
 | **Inputs**       | Source (close)                   |
 | **Parameters**   | `period` (default 5)             |
 | **Outputs**      | Single series (Decay)            |

lib/numerics/edecay/Edecay.md

@@ -2,7 +2,7 @@
 
 | Property         | Value                            |
 | ---------------- | -------------------------------- |
-| **Category**     | Trends (IIR)                     |
+| **Category**     | Numerics                         |
 | **Inputs**       | Source (close)                   |
 | **Parameters**   | `period` (default 5)             |
 | **Outputs**      | Single series (Edecay)           |

lib/trends_FIR/nlma/Nlma.cs

@@ -224,11 +224,12 @@ public sealed class Nlma : AbstractBase
     // ── Weight computation ─────────────────────────────────────────────
 
     /// <summary>
-    /// Computes original Igorad two-phase kernel weights.
+    /// Computes original Igorad two-phase kernel weights (MQL4 NonLagMA v7.1 order).
     /// Phase zone (i=0..period-2): t = i/(period-2), g = t≤0.5 ? 1 : 1/(3πt+1), w = g*cos(πt)
     /// Cycle zone (i=period-1..flen-2): t = 1 + (i-phase+1)*(2*Cycle-1)/(Cycle*period-1), same g/w
     /// Last tap (i=flen-1): weight = 0.
-    /// weights[0] = newest bar, weights[flen-1] = oldest bar.
+    /// weights[0] = newest bar (=1.0), weights[flen-1] = oldest bar (=0.0).
+    /// Matches MQL4 alfa[] order: alfa[0]*Close[0] (newest) .. alfa[Len-1]*Close[Len-1] (oldest).
     /// Returns the signed weight sum for normalization.
     /// </summary>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -238,58 +239,36 @@ public sealed class Nlma : AbstractBase
         int phase = period - 1;
         double coeff = 3.0 * Math.PI;
 
-        // Compute weights in "oldest-first" order (taps[0]=oldest, taps[flen-1]=newest)
-        // then reverse into weights[] so weights[0]=newest, weights[flen-1]=oldest
-        const int StackallocThreshold = 256;
-        double[]? rented = flen > StackallocThreshold ? ArrayPool<double>.Shared.Rent(flen) : null;
-        Span<double> taps = flen <= StackallocThreshold
-            ? stackalloc double[flen]
-            : rented!.AsSpan(0, flen);
-
+        // Compute weights directly in MQL4 alfa[] order:
+        // weights[0] = alfa[0] = weight for newest bar (=1.0 at t=0)
+        // weights[flen-1] = alfa[flen-1] = weight for oldest bar (=0.0)
         double wsum = 0.0;
 
-        try
+        for (int i = 0; i < flen - 1; i++)
         {
-            for (int i = 0; i < flen - 1; i++)
+            double t;
+            if (i <= phase - 1)
             {
-                double t;
-                if (i <= phase - 1)
-                {
-                    // Phase zone: t ramps from 0 to 1
-                    t = phase > 1 ? (double)i / (phase - 1) : 0.0;
-                }
-                else
-                {
-                    // Cycle zone: t continues from 1 upward
-                    double numer = (double)(i - phase + 1) * (2 * Cycle - 1);
-                    double denom = (double)(Cycle * period - 1);
-                    t = 1.0 + (denom > 0 ? numer / denom : 0.0);
-                }
-
-                double beta = Math.Cos(Math.PI * t);
-                double g = t <= 0.5 ? 1.0 : 1.0 / Math.FusedMultiplyAdd(coeff, t, 1.0);
-                double w = g * beta;
-                taps[i] = w;
-                wsum += w;
+                // Phase zone: t ramps from 0 to 1
+                t = phase > 1 ? (double)i / (phase - 1) : 0.0;
+            }
+            else
+            {
+                // Cycle zone: t continues from 1 upward
+                double numer = (double)(i - phase + 1) * (2 * Cycle - 1);
+                double denom = (double)(Cycle * period - 1);
+                t = 1.0 + (denom > 0 ? numer / denom : 0.0);
             }
 
-            // Last tap has weight 0 (original MQL4 loop goes to Len-2)
-            taps[flen - 1] = 0.0;
-
-            // Reverse into weights[]: weights[0]=newest=taps[flen-1], weights[flen-1]=oldest=taps[0]
-            for (int i = 0; i < flen; i++)
-            {
-                weights[i] = taps[flen - 1 - i];
-            }
-        }
-        finally
-        {
-            if (rented != null)
-            {
-                ArrayPool<double>.Shared.Return(rented);
-            }
+            double beta = Math.Cos(Math.PI * t);
+            double g = t <= 0.5 ? 1.0 : 1.0 / Math.FusedMultiplyAdd(coeff, t, 1.0);
+            weights[i] = g * beta;
+            wsum += weights[i];
         }
 
+        // Last tap has weight 0 (original MQL4 loop goes to Len-2)
+        weights[flen - 1] = 0.0;
+
         return wsum;
     }
 
@@ -297,7 +276,8 @@ public sealed class Nlma : AbstractBase
 
     /// <summary>
     /// Convolves when buffer is full (count == flen). Uses precomputed weights.
-    /// weights[0] = newest, weights[flen-1] = oldest. Normalized by signed weight sum.
+    /// weights[0] = newest bar weight (=1.0), weights[flen-1] = oldest bar weight (=0.0).
+    /// Normalized by signed weight sum. Matches MQL4: alfa[0]*Close[0] + ... + alfa[Len-1]*Close[Len-1].
     /// </summary>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private double ConvolveFull()
@@ -307,7 +287,7 @@ public sealed class Nlma : AbstractBase
         int capacity = _buffer.Capacity;
         double sum = 0.0;
 
-        // Iterate oldest-to-newest: oldest bar gets weights[flen-1], newest gets weights[0]
+        // Iterate oldest-to-newest: oldest bar gets weights[flen-1] (≈0), newest gets weights[0] (=1.0)
         int wi = _flen - 1;
         for (int i = head; i < capacity; i++)
         {

lib/trends_IIR/htit/Htit.md

@@ -8,6 +8,8 @@
 | **Outputs**      | Single series (HTIT)                       |
 | **Output range** | Tracks input                     |
 | **Warmup**       | `12` bars                          |
+| **Signature**    | [htit_signature](htit_signature.md) |
+
 
 ### TL;DR
 

lib/trends_IIR/htit/htit_signature.md

@@ -0,0 +1,3 @@
+# HOLT Signature
+
+![HTIT Signature](htit_signature.svg)

lib/trends_IIR/mama/Mama.md

@@ -8,6 +8,8 @@
 | **Outputs**      | Single series (Mama)                       |
 | **Output range** | Tracks input                     |
 | **Warmup**       | `50` bars                          |
+| **Signature**    | [mama_signature](mama_signature.md) |
+
 
 ### TL;DR
 

lib/trends_IIR/mama/mama_signature.md

@@ -0,0 +1,3 @@
+# LTMA Signature
+
+![MAMA Signature](mama_signature.svg)