求教，以下指标计算，为什么MACD输出是空值N/A？

DayBarsAvNum = MAX(DayBarsNumI(0,1),MAX(DayBarsNumI(0,2),DayBarsNumI(0,3)));

   Diff _Nexter = XAverage( Close, 12*DayBarsAvNum) - XAverage( Close,26*DayBarsAvNum) ;    

       Dea_Nexter = XAverage(Diff_Nexter,9*DayBarsAvNum);

       MACD_Nexter = 2*(Diff_Nexter - Dea_Nexter);