Vortex Indicator System for Amibroker (AFL)

// Vortex Indicator 
// S&C Traders Tips Jan 2010 
period = Param("Period" , 14, 2 ); 

VMP = Sum( abs( H - Ref( L, -1 ) ), period ); 
VMM = Sum( abs( L - Ref( H, -1 ) ), period ); 
STR = Sum( ATR( 1 ), period ); 
VIP = VMP / STR; 
VIM = VMM / STR; 
 
Plot( VIP, "VI"+period+ "+", colorBlue); 
Plot( VIM, "VI"+period+ "-", colorRed ); 
 
//The system is defined as:
//- Go long when the VI (or Dmi) goes from less than zero to greater than 
//zero.
//- Go short when the VI (or Dmi) goes from above zero to less than zero.
// - All trades are placed "next day market on open."
// That would translate to:
 
 SetTradeDelays( 1,1,1,1); // everything delayed 1 day
 Buy = VIP > 0 AND Ref(VIP,-1) < 0;
 BuyPrice = Open;
 Sell = VIP < 0 and Ref(VIP,-1) > 0;
 SellPrice = Open;
 Short = Sell;
 Cover = Buy;