What function do I write to step up lot size and step down lot size?

[Tropsmoo]

I'm not sure how to create code for an EA to increase lot size as an account grows and decrease lot size as the account shrinks. So if it starts at $1000 and moves to $2000 the lot size doubles where as if it falls to $500 it cuts in half. 

[Mpho Matela]

double LotAdjust(){
    string baseCurr = StringSubstr(Symbol(),0,3);
    string crossCurr = StringSubstr(Symbol(),3,3);
    double tickValue = SymbolInfoDouble(Symbol(),SYMBOL_TRADE_TICK_VALUE);
    MqlTick last_tick;
    SymbolInfoTick(_Symbol,last_tick);
    double Ask=last_tick.ask;
    // calculate risk based on free margin
    // 
    double riskCapital = AccountInfoDouble(ACCOUNT_MARGIN_FREE) * Risk/100;
    
    if(crossCurr == AccountInfoString(ACCOUNT_CURRENCY)) {
        LTS = (riskCapital / StopLoss) / tickValue;
        Print("Calculated lots (A/C currency = Quote currency): ", LTS);
    } else if(baseCurr == AccountInfoString(ACCOUNT_CURRENCY)) {
        // 
        LTS = ((Ask * riskCapital) / StopLoss) / tickValue;
        Print("Calculated lots (A/C currency = Base currency): ", LTS);
    } else if(crossCurr != AccountInfoString(ACCOUNT_CURRENCY)
           && baseCurr  != AccountInfoString(ACCOUNT_CURRENCY)) {
        LTS = riskCapital / (StopLoss * tickValue);
        Print("Calculated lots (A/C currency neither Base nor Quote currency): ", LTS);
    }
    
    // snap lot size to broker-happy value
    //
    double  lotStep = SymbolInfoDouble(Symbol(),SYMBOL_VOLUME_STEP);
    double  minLot  = SymbolInfoDouble(Symbol(),SYMBOL_VOLUME_MIN);
    LTS            = MathRound(LTS/lotStep) * lotStep;
    
    if(LTS < minLot) {
        LTS = minLot;
    }
    
    return(LTS);

   // another look.....
   /*if (UseMM)Lots=AccountEquity()/Close[0]/1000*Risk/100;
   Lots = arrondirLots(Lots);
   double minLot = MarketInfo(Symbol(), MODE_MINLOT);
   double maxLot = MarketInfo(Symbol(), MODE_MAXLOT);
   if (Lots<minLot)Lots=minLot;
   if (Lots>maxLot)Lots=maxLot;
   */
}

this is what i use...... see its mql5 though, but you can translate it to 4.

[Mpho Matela]

others can help improve it if it does not work for you or you find errors.

[David Diez]

Mpho Matela:
others can help improve it if it does not work for you or you find errors.

//---------------------------------------------- Input parameters ---!
input string         Config_1      = "";       // Money Management
input double         StartLotSize  = 0.01;     // The starting lot size
input double         StartBalance  = 50.0;     // The starting balance
//---------------------------------------------- Money management ---!
double LotsOptimized(){
   double LotStep=MarketInfo(Symbol(),MODE_LOTSTEP),LotSize=0;
   if(LotStep==0.1){LotSize=NormalizeDouble(StartLotSize*(AccountFreeMargin()/StartBalance),1);}
   if(LotStep==0.01){LotSize=NormalizeDouble(StartLotSize*(AccountFreeMargin()/StartBalance),2);}
   if(LotSize<MarketInfo(Symbol(),MODE_MINLOT)){LotSize=MarketInfo(Symbol(),MODE_MINLOT);}
   if(LotSize>MarketInfo(Symbol(),MODE_MAXLOT)){LotSize=MarketInfo(Symbol(),MODE_MAXLOT);}
   return(LotSize);
   }

[Tropsmoo]

Mpho Matela:
this is what i use...... see its mql5 though, but you can translate it to 4.

Thanks for the input, I just sent a private message thinking it was reply, is this put in the trade function category for mql4?

[Tropsmoo]

David Diez:

Thanks for the reply! Is this mql4 or 5? If it's 4, do I input this into the trade function section?