Design map for newbie in mql4

[Hatem Abou Ouf]

Hi,

I am trying to code a user defined function in which I would like to calculate the required lot size of the last martingale order in a cycle to achieve breakeven on certain price , upon reversal.

For example, Buy orders 0, 1,2, and 3 were already opened while the price going down. Now, I want to open Buy 4 order. I need to calculate its size to achieve BE on the red price

I do not need a code but a thinking map of how I can do it. Then, I will try myself and post here to see if it right or wrong. 

Your help is much appreciated

[William Roeder]

Hatem Abou Ouf: I need to calculate its size to achieve BE on the red price

BE (price) is lots weighted average price (Ei loti*pricei)/(Ei loti) Do the algebra.

[Marco vd Heijden]

Hatem Abou Ouf:

Hi,

 a thinking map 

Well the closest to what i can think of is a flow chart here: http://draw.io

[Hatem Abou Ouf]

whroeder1:
BE (price) is lots weighted average price (Ei loti*pricei)/(Ei loti) Do the algebra.

Thank you whroeder1

This is my first trial. If correct, I plan to make my function better by :

1- To make the same function work for both buy and sell cycle orders ( by passing the cycle order type), I think

2- To check better for errors from OrderSelect

This is my first serious week to start mql4 coding just because I like coding!. My plan is to deal with one coding concept per week. ( 15-20 min/daily).

input int BuyMagic = 1111;
//+------------------------------------------------------------------+
//| Expert initialization function                                   |
//+------------------------------------------------------------------+
int OnInit()
  {
//---
   
//---
   return(INIT_SUCCEEDED);
  }
//+------------------------------------------------------------------+
//| Expert deinitialization function                                 |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
  {
//---
   
  }
//+------------------------------------------------------------------+
//| Expert tick function                                             |
//+------------------------------------------------------------------+
void OnTick()
  {
  double BE_Price = 1.2345;
  double Current_BuyOrderLot = AveragePrice_OP_BUY_Orders(BE_Price);
  
   
  }
//+------------------------------------------------------------------+

//---------------------------------------------------------------------------------+
// Calculate the Required lot                                                      |
//---------------------------------------------------------------------------------+
double AveragePrice_OP_BUY_Orders(double BE_Price)
  {
//----
   double Lots   = 0.0;                                      // to calculate the sum of all lots except the current
   double OrderOPrice = 0.0;                                 // to calculate the OP of all open orders
   double LotsPrice = 0.0;                                   // 
   double OP_CurrentBuy = MarketInfo(Symbol(), MODE_BID);    // Open price of the current buy order
   double Average = BE_Price;                         // pass it to the function
   double Required_Lot;
   
   for (int i = OrdersTotal() - 1; i >= 0; i--)
   {
      OrderSelect(i, SELECT_BY_POS, MODE_TRADES);
      if (OrderSymbol() == Symbol() && OrderType() == OP_BUY && OrderMagicNumber() == BuyMagic)
      {
         Lots = Lots + OrderLots();
         LotsPrice = LotsPrice + OrderLots()*OrderOpenPrice();

         Print("Lots : ", OrderLots(), "   OrderOpenPrice : ", OrderOpenPrice());
      }
   }
   Required_Lot = NormalizeDouble (LotsPrice - (Average *Lots)/ (Average - OP_CurrentBuy),Digits) ; // Old Old Old Algebra rusty mind :)
   

//----
   return(Required_Lot);
}

 

[Hatem Abou Ouf]

Oh, I forget to account for the cost of transactions ( Commission and swap). I will try to include that. If you have a clue for me, please do not not hesitate to mention. 

[Hatem Abou Ouf]

Marco vd Heijden:

Well the closest to what i can think of is a flow chart here: http://draw.io

Very interesting tool. Thanks for sharing

[William Roeder]

Hatem Abou Ouf: This is my first trial. If correct, I plan to make my function better by :

Required_Lot = NormalizeDouble (LotsPrice - (Average *Lots)/ (Average - OP_CurrentBuy),Digits);

Close but not quite.

1. Misplaced parenthesis

   BE = (Σ(lot*price) + newLot newPrice) / (Σ(lot) + newLot)
   BE (Σ(lot) + newLot)= (Σ(lot*price) + newLot newPrice)
   BE (Σ(lot) + newLot) - newLot newPrice = Σ(lot*price)
   BE newLot - newLot newPrice = Σ(lot*price) - BE Σ(lot)
   newLot (BE - newPrice) = Σ(lot*price) - BE Σ(lot)
   newLot = {Σ(lot*price) - BE Σ(lot)} / (BE - newPrice)
   
   Required_Lot = {LotsPrice  - Average lots} / (Average - OP_CurrentBuy)

2. Do NOT use NormalizeDouble, EVER. For ANY Reason. It's a kludge, don't use it. It's use is usually wrong, as it is in this case.
   • Print out your values to the precision you want with DoubleToString - Conversion Functions - MQL4 Reference.
   • SL/TP (stops) need to be normalized to tick size (not Point.) (On 5Digit Broker Stops are only allowed to be placed on full pip values. How to find out in mql? - MQL4 and MetaTrader 4 - MQL4 programming forum) and abide by the limits Requirements and Limitations in Making Trades - Appendixes - MQL4 Tutorial and that requires understanding floating point equality Can price != price ? - MQL4 and MetaTrader 4 - MQL4 programming forum
   • Open price for pending orders need to be adjusted. On Currencies, Point == TickSize, so you will get the same answer, but it won't work on Metals. So do it right: Trailing Bar Entry EA - MQL4 and MetaTrader 4 - MQL4 programming forum or Bid/Ask: (No Need) to use NormalizeDouble in OrderSend - MQL4 and MetaTrader 4 - MQL4 programming forum
   • Lot size must also be adjusted to a multiple of LotStep and check against min and max. If that is not a power of 1/10 then NormalizeDouble is wrong. Do it right.