explanation of Stochastic

billysballo 2019.01.15 17:03

Hi,

In the Stochastic Indicator that you can find in MT4, there is a recurring if statement

pos=InpKPeriod-1;
if(pos+1<prev_calculated)
      pos=prev_calculated-2;

which I do not understand. Why does it subtract -2 ? what the point of the code above?

This is the onCalculate() function to give a bit more of context around the code above:

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[])
  {
   int    i,k,pos;
//--- check for bars count
   if(rates_total<=InpKPeriod+InpDPeriod+InpSlowing)
      return(0);
//--- counting from 0 to rates_total
   ArraySetAsSeries(ExtMainBuffer,false);
   ArraySetAsSeries(ExtSignalBuffer,false);
   ArraySetAsSeries(ExtHighesBuffer,false);
   ArraySetAsSeries(ExtLowesBuffer,false);
   ArraySetAsSeries(low,false);
   ArraySetAsSeries(high,false);
   ArraySetAsSeries(close,false);
//---
   pos=InpKPeriod-1;
   if(pos+1<prev_calculated)
      pos=prev_calculated-2;
   else
     {
      for(i=0; i<pos; i++)
        {
         ExtLowesBuffer[i]=0.0;
         ExtHighesBuffer[i]=0.0;
        }
     }
//--- calculate HighesBuffer[] and ExtHighesBuffer[]
   for(i=pos; i<rates_total && !IsStopped(); i++)
     {
      double dmin=1000000.0;
      double dmax=-1000000.0;
      for(k=i-InpKPeriod+1; k<=i; k++)
        {
         if(dmin>low[k])
            dmin=low[k];
         if(dmax<high[k])
            dmax=high[k];
        }
      ExtLowesBuffer[i]=dmin;
      ExtHighesBuffer[i]=dmax;
     }
//--- %K line
   pos=InpKPeriod-1+InpSlowing-1;
   if(pos+1<prev_calculated)
      pos=prev_calculated-2;
   else
     {
      for(i=0; i<pos; i++)
         ExtMainBuffer[i]=0.0;
     }
//--- main cycle
   for(i=pos; i<rates_total && !IsStopped(); i++)
     {
      double sumlow=0.0;
      double sumhigh=0.0;
      for(k=(i-InpSlowing+1); k<=i; k++)
        {
         sumlow +=(close[k]-ExtLowesBuffer[k]);
         sumhigh+=(ExtHighesBuffer[k]-ExtLowesBuffer[k]);
        }
      if(sumhigh==0.0)
         ExtMainBuffer[i]=100.0;
      else
         ExtMainBuffer[i]=sumlow/sumhigh*100.0;
     }
//--- signal
   pos=InpDPeriod-1;
   if(pos+1<prev_calculated)
      pos=prev_calculated-2;
   else
     {
      for(i=0; i<pos; i++)
         ExtSignalBuffer[i]=0.0;
     }
   for(i=pos; i<rates_total && !IsStopped(); i++)
     {
      double sum=0.0;
      for(k=0; k<InpDPeriod; k++)
         sum+=ExtMainBuffer[i-k];
      ExtSignalBuffer[i]=sum/InpDPeriod;
     }
//--- OnCalculate done. Return new prev_calculated.
   return(rates_total);
  }