各位兄台帮我看看 无法识别的字符串 谢谢

Params Numeric Length(26); Numeric StdDevUp(2.0); Numeric StdDevDn(-2.0); Numeric Lots(1); Vars Numeric UpperBand; Numeric LowerBand; Series<Numeric> MidLine; Numeric StdValue; MidLine=Average(Close[1],Length); //编译不过，显示无法识别的字MidLine StdValue = StandardDev(Close[1],Length); UpperBand= MidLine+StdDevUp*StdValue; LowerBand= MidLine-StdDevUp*StdValue; PlotNumeric("UpperBand",UpperBand); PlotNumeric("LowerBand",LowerBand); PlotNumeric(" MidLine", MidLine); If(MarketPosition!=1 &&CrossOver(Close[1],UpperBand)) { Buy(Lots,Open); } If(MarketPosition!=-1 &&CrossUnder(Close[1],LowerBand)) { SellShort(Lots,Open); } If(MarketPosition==1 && Close[1]< MidLine[1]) { Sell(Lots,Open); } If(MarketPosition==-1 && Close[1]> MidLine[1]) { BuyToCover(Lots,Open); } 编译不过，显示无法识别的字符串MidLine