编译报错:数组或序列变量回溯数量与定义类型不匹配

代码是：Params Numeric FastLength(12); Numeric SlowLength(26); Numeric MACDLength(9);Vars Numeric MACDDiff; Numeric AvgMACD; Numeric MACDValue;Events OnReady() { } OnBar(ArrayRef<Integer> indexs) { Range[0:DataCount-1] { MACDDiff = XAverage( Close, FastLength ) - XAverage( Close, SlowLength ) ; AvgMACD = XAverage(MACDDiff,MACDLength); MACDValue = MACDDiff - AvgMACD; } print(Text(MACDValue)); print(Text(data1.MACDValue)); print(Text(data2.MACDValue)); print(Text(data1.MACDValue[1]));}报错：请问官方大佬，我想回溯前N根bar的MACDValue，要怎么获得呢？ 不管是前一根或者前10根的值都行。