How to Build an Expert Advisor Based on the Gator Oscillator in Mql4

Here is a complete, fully functional trading strategy based on the Bill Williams Gator Oscillator for MetaTrader 4.

Strategy Logic: "Gator Eating" Trend Follower

This strategy attempts to capture trends when the Gator Oscillator is in its "Eating" phase (expansion) and the price confirms the direction relative to the Alligator lines.

1. Indicators Used:

   • Gator Oscillator: Used to determine market volatility phases (Sleeping, Awakening, Eating, Sated).
   • Alligator: Used to determine trend direction and support/resistance levels.

2. Entry Conditions:

   • Long (Buy):
     • Gator Expansion: Both the Upper and Lower Gator histograms are Green (Current value > Previous value). This indicates the "Eating" phase.
     • Trend Confirmation: The Close price of the previous bar is above the Alligator's Teeth (Red Line).
   • Short (Sell):
     • Gator Expansion: Both the Upper and Lower Gator histograms are Green.
     • Trend Confirmation: The Close price of the previous bar is below the Alligator's Teeth (Red Line).

3. Exit Conditions:

   • Stop Loss: Fixed pip value provided in inputs.
   • Take Profit: Fixed pip value provided in inputs.
   • Trailing Stop: The Stop Loss dynamically trails along the Alligator's Jaw (Blue Line). This allows the trade to ride the trend until the trend structure breaks.

MQL4 Code

//+------------------------------------------------------------------+
//|                                                GatorStrategy.mq4 |
//|                                     Copyright 2023, MetaQuotes   |
//|                                             https://www.mql5.com |
//+------------------------------------------------------------------+
#property copyright "Copyright 2023, Quantitative AI Assistant"
#property link      "https://www.mql5.com"
#property version   "1.00"
#property strict

//--- Input Parameters
input string   _       = "--- Trade Settings ---";
input double   LotSize = 0.1;             // Fixed Lot Size
input int      MagicNumber = 123456;      // Magic Number ID
input int      Slippage = 3;              // Max Slippage in pips

input string   __      = "--- Risk Management ---";
input int      StopLoss = 50;             // Stop Loss in pips (0 = None)
input int      TakeProfit = 100;          // Take Profit in pips (0 = None)
input bool     UseTrailing = true;        // Enable Trailing Stop based on Alligator Jaw

input string   ___     = "--- Alligator Settings ---";
input int      JawPeriod = 13;            // Blue Line Period
input int      JawShift = 8;              // Blue Line Shift
input int      TeethPeriod = 8;           // Red Line Period
input int      TeethShift = 5;            // Red Line Shift
input int      LipsPeriod = 5;            // Green Line Period
input int      LipsShift = 3;             // Green Line Shift
input ENUM_MA_METHOD MaMethod = MODE_SMMA;// MA Method
input ENUM_APPLIED_PRICE AppliedPrice = PRICE_MEDIAN; // Applied Price

//--- Global Variables
double g_point;

//+------------------------------------------------------------------+
//| Expert initialization function                                   |
//+------------------------------------------------------------------+
int OnInit()
{
   // Normalize point value for 3/5 digit brokers
   if(Digits == 3 || Digits == 5) g_point = Point * 10;
   else g_point = Point;
   
   return(INIT_SUCCEEDED);
}

//+------------------------------------------------------------------+
//| Expert deinitialization function                                 |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
{
   // Clean up if necessary
}

//+------------------------------------------------------------------+
//| Expert tick function                                             |
//+------------------------------------------------------------------+
void OnTick()
{
   // 1. Check for Open Positions
   if(OrdersTotal() > 0)
   {
      ManageOpenPositions();
   }

   // 2. Check for New Bar (Entry logic runs once per bar close)
   static datetime lastBarTime = 0;
   if(Time[0] == lastBarTime) return;
   lastBarTime = Time[0];

   // 3. Check Entry Conditions if no orders are open for this symbol/magic
   if(CountOrders() == 0)
   {
      CheckEntrySignals();
   }
}

//+------------------------------------------------------------------+
//| Check for Entry Signals                                          |
//+------------------------------------------------------------------+
void CheckEntrySignals()
{
   // --- Get Gator Oscillator Values (Bar 1 and Bar 2) ---
   // MODE_UPPER = 1, MODE_LOWER = 2
   double gatorUp1 = iGator(NULL, 0, JawPeriod, JawShift, TeethPeriod, TeethShift, LipsPeriod, LipsShift, MaMethod, AppliedPrice, MODE_UPPER, 1);
   double gatorUp2 = iGator(NULL, 0, JawPeriod, JawShift, TeethPeriod, TeethShift, LipsPeriod, LipsShift, MaMethod, AppliedPrice, MODE_UPPER, 2);
   
   double gatorLow1 = iGator(NULL, 0, JawPeriod, JawShift, TeethPeriod, TeethShift, LipsPeriod, LipsShift, MaMethod, AppliedPrice, MODE_LOWER, 1);
   double gatorLow2 = iGator(NULL, 0, JawPeriod, JawShift, TeethPeriod, TeethShift, LipsPeriod, LipsShift, MaMethod, AppliedPrice, MODE_LOWER, 2);

   // --- Determine Gator Colors (Green = Expansion, Red = Contraction) ---
   // Green means current value > previous value (absolute values)
   bool isUpGreen = (gatorUp1 > gatorUp2);
   bool isLowGreen = (gatorLow1 > gatorLow2);
   
   // "Eating" Phase: Both bars are Green
   bool isGatorEating = isUpGreen && isLowGreen;

   // --- Get Alligator Teeth (Red Line) for Trend Confirmation ---
   double teeth = iAlligator(NULL, 0, JawPeriod, JawShift, TeethPeriod, TeethShift, LipsPeriod, LipsShift, MaMethod, AppliedPrice, MODE_GATORTEETH, 1);
   double closePrice = iClose(NULL, 0, 1);

   // --- Execution Logic ---
   if(isGatorEating)
   {
      // Buy Signal: Gator Eating + Price Closed Above Teeth
      if(closePrice > teeth)
      {
         double sl = (StopLoss > 0) ? Ask - StopLoss * g_point : 0;
         double tp = (TakeProfit > 0) ? Ask + TakeProfit * g_point : 0;
         
         int ticket = OrderSend(Symbol(), OP_BUY, LotSize, Ask, Slippage, sl, tp, "Gator Buy", MagicNumber, 0, clrGreen);
         if(ticket < 0) Print("OrderSend Failed: ", GetLastError());
      }
      // Sell Signal: Gator Eating + Price Closed Below Teeth
      else if(closePrice < teeth)
      {
         double sl = (StopLoss > 0) ? Bid + StopLoss * g_point : 0;
         double tp = (TakeProfit > 0) ? Bid - TakeProfit * g_point : 0;
         
         int ticket = OrderSend(Symbol(), OP_SELL, LotSize, Bid, Slippage, sl, tp, "Gator Sell", MagicNumber, 0, clrRed);
         if(ticket < 0) Print("OrderSend Failed: ", GetLastError());
      }
   }
}

//+------------------------------------------------------------------+
//| Manage Open Positions (Trailing Stop)                            |
//+------------------------------------------------------------------+
void ManageOpenPositions()
{
   if(!UseTrailing) return;

   // Get Alligator Jaw (Blue Line) value for trailing
   // We use shift 1 (previous closed bar) to ensure the line value is fixed
   double jaw = iAlligator(NULL, 0, JawPeriod, JawShift, TeethPeriod, TeethShift, LipsPeriod, LipsShift, MaMethod, AppliedPrice, MODE_GATORJAW, 1);

   for(int i = 0; i < OrdersTotal(); i++)
   {
      if(OrderSelect(i, SELECT_BY_POS, MODE_TRADES))
      {
         if(OrderSymbol() == Symbol() && OrderMagicNumber() == MagicNumber)
         {
            // Trailing for Buy
            if(OrderType() == OP_BUY)
            {
               // Ensure Jaw is above open price (in profit) or just trail strictly
               // Here we trail if Jaw is higher than current SL
               if(jaw > OrderStopLoss() && jaw < Bid) 
               {
                  // Keep a minimum distance of 1 spread or 5 points to avoid stop hunting
                  double minStop = MarketInfo(Symbol(), MODE_STOPLEVEL) * Point;
                  if(Bid - jaw > minStop)
                  {
                     if(!OrderModify(OrderTicket(), OrderOpenPrice(), NormalizeDouble(jaw, Digits), OrderTakeProfit(), 0, clrBlue))
                        Print("Trailing Buy Failed: ", GetLastError());
                  }
               }
            }
            // Trailing for Sell
            if(OrderType() == OP_SELL)
            {
               // Trail if Jaw is lower than current SL (or SL is 0)
               if((jaw < OrderStopLoss() || OrderStopLoss() == 0) && jaw > Ask)
               {
                  double minStop = MarketInfo(Symbol(), MODE_STOPLEVEL) * Point;
                  if(jaw - Ask > minStop)
                  {
                     if(!OrderModify(OrderTicket(), OrderOpenPrice(), NormalizeDouble(jaw, Digits), OrderTakeProfit(), 0, clrRed))
                        Print("Trailing Sell Failed: ", GetLastError());
                  }
               }
            }
         }
      }
   }
}

//+------------------------------------------------------------------+
//| Count Open Orders for this EA                                    |
//+------------------------------------------------------------------+
int CountOrders()
{
   int count = 0;
   for(int i = 0; i < OrdersTotal(); i++)
   {
      if(OrderSelect(i, SELECT_BY_POS, MODE_TRADES))
      {
         if(OrderSymbol() == Symbol() && OrderMagicNumber() == MagicNumber)
            count++;
      }
   }
   return count;
}
//+------------------------------------------------------------------+

How to Install and Use

1. Open MetaEditor: In MT4, press F4.
2. Create New: Click New -> Expert Advisor (template) -> Name it "GatorStrategy".
3. Paste Code: Delete everything in the new file and paste the code provided above.
4. Compile: Press F7. Ensure there are no errors in the "Errors" tab at the bottom.
5. Backtest: Go to MT4, press Ctrl+R to open the Strategy Tester. Select "GatorStrategy", choose a symbol (e.g., EURUSD), a timeframe (H1 or H4 is recommended for Bill Williams strategies), and click Start.

Key Strategy Details

• Gator Logic: The code calculates iGator for the previous bar (index 1) and the bar before that (index 2). If the value at index 1 is greater than index 2, the bar is considered "Green". We require both the Upper and Lower histograms to be Green to confirm strong momentum.
• Trailing Stop: The strategy uses the Alligator's Jaw (Blue Line) as a dynamic Stop Loss. This is a classic trend-following technique. As the trend progresses, the Blue line moves closer to the price, locking in profits.
• Risk Management: The strategy uses a fixed lot size but includes Stop Loss and Take Profit inputs to protect capital if the trend reverses immediately.

Q&A

Q: Why do you use MODE_GATORTEETH for the trend filter?
A: In Bill Williams' theory, the Teeth (Red Line) represents the "Balance Line" for the current timeframe. Price closing above/below it is a standard confirmation that the immediate trend is valid.

Q: Can I use this on M1 or M5 timeframes?
A: While the code will run, Gator and Alligator strategies are momentum-based and typically perform poorly on very low timeframes due to noise and spread costs. H1, H4, and Daily charts usually yield better results with this logic.

Q: What does g_point do?
A: This variable automatically adjusts the pip calculations for 5-digit brokers (where 1 pip = 10 points) and 4-digit brokers, ensuring that a 50 pip Stop Loss is actually 50 pips, not 5.