TRIX in MetaTrader 5 — MQL5 Source Code

TRIX in MQL5 is a nice exercise in chaining smoothing buffers — an EMA of an EMA of an EMA, then a rate of change. See the explainer for the concept.

What you’ll need

• MetaTrader 5 with MetaEditor
• Save as AlgoGen.TRIX.mq5 under MQL5/Indicators/

The source

//+------------------------------------------------------------------+
//|                                                 AlgoGen.TRIX.mq5 |
//|                                          Copyright 2026, AlgoGen |
//|                                           https://www.algogen.io |
//+------------------------------------------------------------------+
#property copyright "Copyright 2026, AlgoGen"
#property link      "https://www.algogen.io"
#property version   "1.00"
#property indicator_separate_window
#property indicator_buffers 5
#property indicator_plots   2

#property indicator_label1  "TRIX"
#property indicator_type1   DRAW_LINE
#property indicator_color1  clrDodgerBlue
#property indicator_width1  2
#property indicator_label2  "Signal"
#property indicator_type2   DRAW_LINE
#property indicator_color2  clrOrangeRed
#property indicator_level1  0.0

input int InpPeriod = 15;
input int InpSignal = 9;

double TrixBuffer[], SigBuffer[], E1[], E2[], E3[];

int OnInit()
  {
   SetIndexBuffer(0, TrixBuffer, INDICATOR_DATA);
   SetIndexBuffer(1, SigBuffer,  INDICATOR_DATA);
   SetIndexBuffer(2, E1, INDICATOR_CALCULATIONS);
   SetIndexBuffer(3, E2, INDICATOR_CALCULATIONS);
   SetIndexBuffer(4, E3, INDICATOR_CALCULATIONS);
   IndicatorSetString(INDICATOR_SHORTNAME,
      StringFormat("AlgoGen TRIX(%d,%d)", InpPeriod, InpSignal));
   return(INIT_SUCCEEDED);
  }

// One recursive EMA step: dst[i] from src[i] and dst[i-1].
void EmaStep(const double &src[], double &dst[], int i, int period)
  {
   double k = 2.0 / (period + 1.0);
   dst[i] = (i == 0) ? src[i] : src[i] * k + dst[i - 1] * (1.0 - k);
  }

int OnCalculate(const int rates_total, const int prev_calculated,
                const datetime &time[], const double &open[],
                const double &high[],   const double &low[],
                const double &close[],  const long &tick_volume[],
                const long &volume[],   const int &spread[])
  {
   if(rates_total < 2) return(0);
   int start = (prev_calculated > 1) ? prev_calculated - 1 : 0;

   for(int i = start; i < rates_total; i++)
     {
      EmaStep(close, E1, i, InpPeriod);
      EmaStep(E1,    E2, i, InpPeriod);
      EmaStep(E2,    E3, i, InpPeriod);
      TrixBuffer[i] = (i > 0 && E3[i - 1] != 0.0)
                      ? 100.0 * (E3[i] - E3[i - 1]) / E3[i - 1] : 0.0;
      double k = 2.0 / (InpSignal + 1.0);
      SigBuffer[i] = (i == 0) ? TrixBuffer[0]
                     : TrixBuffer[i] * k + SigBuffer[i - 1] * (1.0 - k);
     }
   return(rates_total);
  }
//+------------------------------------------------------------------+

Install & compile

1. Drop it in MQL5/Indicators/, press F7.
2. Drag onto a chart — a separate window shows the TRIX and signal lines around zero, matching the output chart.

Gotchas

• Chained calculation buffers. E1, E2, E3 are INDICATOR_CALCULATIONS buffers holding the successive smoothings — the clean way to build an EMA of an EMA of an EMA in MQL5.
• Order of operations. Smooth three times, then take the rate of change of the third EMA. Doing the ROC earlier gives a different indicator.
• MQL4. Same math; swap the OnCalculate signature and buffer setup. There’s no standard built-in TRIX, so the custom version is the way.

Same indicator elsewhere: Python, Pine Script, EasyLanguage, NinjaScript. Then test a TRIX rule in AlgoGen.

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This post is educational, not financial advice. Indicators describe the past; they don’t predict the future. Backtest anything before you risk real money on it.