//+------------------------------------------------------------------+
//|                                                        Trend.mq5 |
//|                                                        AIS Forex |
//|                        https://www.mql5.com/ru/users/aleksej1966 |
//+------------------------------------------------------------------+
#property copyright "AIS Forex"
#property link      "https://www.mql5.com/ru/users/aleksej1966"
#property version   "1.00"
#property indicator_separate_window
#property indicator_buffers 1
#property indicator_plots   1

#property indicator_type1  DRAW_LINE
#property indicator_label1 "Trend"
#property indicator_color1 clrBlue
#property indicator_width1 1
#property indicator_style1 STYLE_SOLID

input ushort iPeriod=24;
int period;
double buffer[];
//+------------------------------------------------------------------+
//| Custom indicator initialization function                         |
//+------------------------------------------------------------------+
int OnInit()
  {
//--- indicator buffers mapping
   SetIndexBuffer(0,buffer,INDICATOR_DATA);
   ArraySetAsSeries(buffer,true);

   period=MathMax(1,iPeriod);
//---
   return(INIT_SUCCEEDED);
  }
//+------------------------------------------------------------------+
//| Custom indicator iteration function                              |
//+------------------------------------------------------------------+
int OnCalculate(const int rates_total,
                const int prev_calculated,
                const datetime &time[],
                const double &open[],
                const double &high[],
                const double &low[],
                const double &close[],
                const long &tick_volume[],
                const long &volume[],
                const int &spread[])
  {
//---
   if(rates_total>prev_calculated)
     {
      ArraySetAsSeries(open,true);

      int bars=prev_calculated>0?rates_total-prev_calculated-1:rates_total-period-2;

      for(int i=bars;i>=0;i--)
        {
         double sma=0;
         for(int j=1;j<=period;j++)
            sma=sma+open[i+j];

         buffer[i]=(open[i]-sma/period+buffer[i+1])/2; 
        }
     }
//--- return value of prev_calculated for next call
   return(rates_total);
  }
//+------------------------------------------------------------------+