Figurelli RSI

//+------------------------------------------------------------------+
//|                                                Figurelli RSI.mq4 |
//|                              Copyright © 2011, Rogerio Figurelli |
//|                                       http://www.trajecta.com.br |
//+------------------------------------------------------------------+
#property copyright "Copyright © 2011, Rogerio Figurelli"
#property link      "http://www.trajecta.com.br"

#property indicator_separate_window
#property indicator_minimum 0
#property indicator_maximum 100
#property indicator_buffers 1
#property indicator_color1 Red

//---- input parameters
extern int period=120;
extern int gain=10;

//---- global vars
static double buffer_indicator[];
static double buffer_positive[];
static double buffer_negative[];
static string name;

//+------------------------------------------------------------------+
//| Initialization                                                   |
//+------------------------------------------------------------------+
int init() {
   IndicatorBuffers(3);
   SetIndexStyle(0,DRAW_LINE);
   SetIndexBuffer(0,buffer_indicator);
   name="Figurelli RSI ("+period+","+gain+")";
   IndicatorShortName(name);
   SetIndexLabel(0,name);
   SetIndexDrawBegin(0,period);
   SetIndexBuffer(1,buffer_positive);
   SetIndexBuffer(2,buffer_negative);
   return(0);
}
//+------------------------------------------------------------------+
//| Figurelli Relative Strength Index                                |
//+------------------------------------------------------------------+
int start() {
   int i,j;
   int counted_bars=IndicatorCounted();
   double diff;
   double negative,n;
   double positive,p;

   if (Bars<=period) return(0);
   if (counted_bars<1) {
      for (i=1;i<=period;i++)
         buffer_indicator[Bars-i]=0;
   }
   i=Bars-period-1;
   if (counted_bars>=period)
      i=Bars-counted_bars-1;
   while (i>=0) {
      n=0;
      p=0;
      if (i==(Bars-period-1)) {
         j=Bars-2;
         while (j>=i) {
            diff=Close[j]-Close[j+1];
            if (diff>0) 
               p+=diff; 
            else 
               n-=diff;
            j--;
         }
         positive=p/period;
         negative=n/period;
      }
      else {
         diff=Close[i]-Close[i+1];
         if (diff>0) 
            p=diff; 
         else 
            n=-diff;
         positive=(buffer_positive[i+1]*(period-1)+p)/period;
         negative=(buffer_negative[i+1]*(period-1)+n)/period;
      }
      buffer_positive[i]=positive;
      buffer_negative[i]=negative;
      if (negative==0) 
         buffer_indicator[i]=0;
      else 
         buffer_indicator[i]=100-100/(1+positive/negative);
      buffer_indicator[i]-=50;
      buffer_indicator[i]*=gain;
      if (buffer_indicator[i]<-50) 
         buffer_indicator[i]=-50;
      if (buffer_indicator[i]>50) 
         buffer_indicator[i]=50;
      buffer_indicator[i]+=50;
      i--;
   }
   return(0);
}
//+------------------------------------------------------------------+