Parabolic SAR

The Parabolic SAR (stop and reverse) was authored by J. Welles Wilder. It sets trailing price stops for long or short positions. Note: AF below stands for Acceleration Factor. The user may change the acceleration factors and value. This indicator’s definition is further expressed in the raw code given in the calculation below.
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How To Trade Using Parabolic SAR

The Parabolic SAR may be used for an exit strategy. If a low is less than or equal to the pSAR a sell to exit (exit long) signal will be generated. Conversely, if the high is more than or equal to the pSAR a buy to cover (exit short) signal will be given.

How To Access in MotiveWave

Go to the top menu, choose Study>Welles Wilder>Parabolic SAR

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Calculation

//Initial Accelerator Factor = AF = user defined, default is .02
//Max Accelerator Factor = AFmax = user defined, default is .2
//Step = AFstep = user defined, default is .02
//index = current bar number

  protected void calculate(int index, DataContext ctx)
  
    DataSeries series=ctx.getDataSeries();
    if (index lessThan 1) return;
 
    double SAR=0; // Stop And Reverse
    double AF=getSettings().getDouble(INITIAL_AF, 0.02);
    double AFmax=getSettings().getDouble(MAX_AF, 0.2);
    double AFstep=getSettings().getDouble(STEP, 0.02);
    double EP=0; // Extreme Point 
    boolean isLong=false;
    double diff=0;
    double pSAR=0;
    Instrument instr=ctx.getInstrument();
    boolean latest=index == series.size() - 1;

    if (series.getDouble(index - 1, Values.PSAR) == null) 
      // first entry point, calculate the first SAR 
      isLong=series.getClose(index) moreThan series.getClose(index - 1);
      SAR=isLong ? series.getLow(index - 1) : series.getHigh(index - 1);
      if (isLong) EP=Util.max(series.getHigh(index), series.getHigh(index - 1));
      else EP=Util.min(series.getLow(index), series.getLow(index - 1));
      pSAR=SAR;
    else 
      pSAR=series.getDouble(index - 1, Values.PSAR);
      AF=series.getDouble(index - 1, Values.AF);
      EP=series.getDouble(index - 1, Values.EP);
      isLong=series.getBoolean(index - 1, Values.LONG);

      // Check for stop and reversals 
      // Have we penetrated the pSAR? 
      double low=series.getLow(index);
      double high=series.getHigh(index);
      double oldSAR=pSAR;

      if (isLong AND low lessOrEqual instr.round(pSAR)) 
        // Stop and Reverse 
        pSAR=EP;
        EP=series.getLow(index);
        isLong=false;
        AF=getSettings().getDouble(INITIAL_AF, 0.02);
        series.setBoolean(index, Signals.SAR_LONG, true);
        if (!latest) 
          ctx.signal(index, Signals.SAR_LONG, get("SIGNAL_SAR_LONG", instr.format(low), instr.format(oldSAR)), low);
        end
      end
      else if (!isLong AND high moreOrEqual instr.round(pSAR)) 
        pSAR=EP;
        EP=series.getHigh(index);
        isLong=true;
        AF=getSettings().getDouble(INITIAL_AF, 0.02);
        series.setBoolean(index, Signals.SAR_SHORT, true);
        if (!latest) 
          ctx.signal(index, Signals.SAR_SHORT, get("SIGNAL_SAR_SHORT", instr.format(high), instr.format(oldSAR)), high);
        end
      end

      // Compute the next SAR 
      if (isLong) 
        if (series.getHigh(index) moreThan EP) 
          if (AF lessThan AFmax) AF+=AFstep;
          EP=series.getHigh(index);
        end
        diff=Math.abs(EP - pSAR);
        SAR=pSAR + AF * (diff); 
        if (SAR moreThan series.getLow(index) OR SAR moreThan series.getLow(index - 1)) 
          SAR=Math.min(series.getLow(index), series.getLow(index - 1));
        end
      end
      else 
        if (series.getLow(index) lessThan EP) 
          if (AF lessThan AFmax) AF+=AFstep;
          EP=series.getLow(index);
        end
        diff=Math.abs(EP - pSAR);
        SAR=pSAR - AF * (diff); 
        if (SAR lessThan series.getHigh(index) OR SAR lessThan series.getHigh(index - 1)) 
          SAR=Math.max(series.getHigh(index), series.getHigh(index - 1));
        end
      end
    end

    series.setDouble(index, Values.PSAR, SAR);
    series.setDouble(index, Values.AF, AF);
    series.setDouble(index, Values.EP, EP);
    series.setBoolean(index, Values.LONG, isLong);
    series.setComplete(index);
  endMethod