code: public static double simpleExponentialSmoothingQuick(double Ytminus1, double Stminus1, double a) {
          double EMA=a*Ytminus1+(1-a)*Stminus1;
  
          return EMA;
      }
docs: Simple Explonential Smoothing: Calculates Ft+1 by using previous results. A quick version of the simpleExponentialSmoothing
  
  @param Ytminus1
  @param Stminus1
  @param a
  @return