Profit Risk Method [PRM]

Summary:
This position sizing script risks a specified fraction of the account equity on each trade, it does so by using a percentage of the starting account equity plus a percentage of the total closed trade profit.

	 ' Assign the parameters to script variables.
	_accountFraction = accountFraction
	_profitsFraction = profitsFraction
	_defaultRiskPerTrade = defaultRiskPerTrade
	_enableExitSizing = enableExitSizing
	

	 ' Get the order type.
	Define typeOrder As Integer = OrderType(orderIndex)
	 ' Get the order symbol index.
	Define symbolIndex As Integer = OrderSymbolIndex(orderIndex)
	 ' If the order type is an entry order then calculate the position size.
	If (typeOrder = C_BUY Or _
		typeOrder = C_SELL_SHORT) Then
		StatsRequest(DateTimeStart(), DateTimeCurrent(),True,True,True,True, True)
		 ' Calculate the total amount of equity to risk on a single trade.
		Define totalRisk As Number = StatsStartingEquity() * _accountFraction + StatsNetProfit () * _profitsFraction
		 ' Assign the default minimum risk per trade.
		Define riskPerTrade As Number = -1 * _defaultRiskPerTrade
		 ' Get the closed trades indexes.
		Define closedTrades() As Integer = TradeIndexList(C_CLOSED)
		 ' Use for the P/L of the current trade.
		Define profitLoss As Number
		 ' Iterate over all of the closed trades.
		For i As Integer = 0 To closedTrades.Length - 1
			 ' Get the P/L of the current closed trade.
			profitLoss  = TradeProfitLoss(closedTrades(i))
			 ' Keep track of the largest loss.
			If (profitLoss < riskPerTrade) Then
				riskPerTrade = profitLoss
			End If
		Next
		Return MathFloor(totalRisk / MathAbs(riskPerTrade))
	Else If (_enableExitSizing)
		 ' If the order type is an exit order then calculate the position size.
		Define openPositions() As Integer = PositionIndexList(C_OPEN)
		For i As Integer = 0 To openPositions.Length - 1
			If (PositionSymbolIndex(openPositions(i)) = symbolIndex) Then
				Return PositionQuantity(openPositions(i))
			End If
		Next
	End If