//+------------------------------------------------------------------+
//|                                       Linear Regression Line.mq4 |
//+------------------------------------------------------------------+
#property copyright "MetaTrader 4"
#property link      "http://metatrader.com"
//---- indicator settings
#property indicator_chart_window
#property indicator_buffers 1
#property indicator_color1 Blue
#property indicator_width1 2
//---- input parameters
extern int LRLPeriod=21;
extern string  p = "--Applied Price Types--";
extern string  p0 = " 0 = close";
extern string  p1 = " 1 = open";
extern string  p2 = " 2 = high";
extern string  p3 = " 3 = low";
extern string  p4 = " 4 = median(high+low)/2";
extern string  p5 = " 5 = typical(high+low+close)/3";
extern string  p6 = " 6 = weighted(high+low+close+close)/4";
extern int       MAAppliedPrice = 0;
//---- buffers
double LRLBuffer[];

int shift=0;
int n=0;
double sumx=0, sumy=0, sumxy=0, sumx2=0, sumy2=0;
double m=0, yint=0, r=0;
//+------------------------------------------------------------------+
//| Custom indicator initialization function                         |
//+------------------------------------------------------------------+
int init()
  {
//---- indicators
   SetIndexStyle(0,DRAW_LINE);
   SetIndexBuffer(0,LRLBuffer);
   IndicatorDigits(Digits);
   if(LRLPeriod < 2) LRLPeriod = 2;
   IndicatorShortName("Linear Regression Line ("+LRLPeriod+")");
   SetIndexDrawBegin(0,LRLPeriod+2);
   IndicatorDigits(MarketInfo(Symbol(),MODE_DIGITS)+4);
//----
   return(0);
  }
//+------------------------------------------------------------------+
//| Custom indicator deinitialization function                       |
//+------------------------------------------------------------------+
int deinit()
  {
   return(0);
  }
//+------------------------------------------------------------------+
//| Linear Regression Line                                           |
//+------------------------------------------------------------------+
int start()
  {
   double myPrice;
   int limit;
   int counted_bars=IndicatorCounted();
   if(counted_bars<0) counted_bars=0;
   if(counted_bars>0) counted_bars--;
   limit=Bars-counted_bars;

   for(int shift=limit-1; shift>=0; shift--)
      {
         sumx = 0;
         sumy = 0;
         sumxy = 0;
         sumx2 = 0;
         sumy2 = 0;
         for(n = 0; n <= LRLPeriod-1; n++)
             { 
               myPrice = Price(MAAppliedPrice, shift+n);
               sumx = sumx + n;
               sumy = sumy + myPrice;
               sumxy = sumxy + n * myPrice;
               sumx2 = sumx2 + n * n;
               sumy2 = sumy2 + myPrice * myPrice; 
             }                      
         m=(LRLPeriod*sumxy-sumx*sumy)/(LRLPeriod*sumx2-sumx*sumx); 
         yint=(sumy+m*sumx)/LRLPeriod;
         r=(LRLPeriod*sumxy-sumx*sumy)/MathSqrt((LRLPeriod*sumx2-sumx*sumx)*(LRLPeriod*sumy2-sumy*sumy)); 
         LRLBuffer[shift]=MathFloor((yint-m*LRLPeriod)/Point) * Point;
      }
   return(0);
  }

double Price(int prMode, int myShift)
{

   double pr;
   switch (prMode)
   {
     case 0: pr = Close[myShift];break;
     case 1: pr = Open[myShift];break;
     case 2: pr = High[myShift];break;
     case 3: pr = Low[myShift];break;
     case 4: pr = (High[myShift] + Low[myShift])/2;break;
     case 5: pr = (High[myShift] + Low[myShift] + Close[myShift])/3;break;
     case 6: pr = (High[myShift] + Low[myShift] + 2 * Close[myShift])/4;break;
   }
     
     return (pr);
}

//+------------------------------------------------------------------+