plot.line plot.clear

请问: 任意品种、周期加载1000个bar，然后在 第898 899 900的位置，用 plot.line 画三次线段，在901的位置如何用 plot.clear 删除掉这三个线段？谢谢！代码如下：这样写只能删掉898的位置画的线段，后面899 900两次还是会保留。Params Numeric FastLength(5);// 短期指数平均线参数 Numeric SlowLength(20);// 长期指数平均线参数 Vars Series<Numeric> AvgValue1; Series<Numeric> AvgValue2; Plot plt; Array<Numeric> x1Data;//x轴数据集 Array<Numeric> y1Data;//y轴数据集 Events OnBar(ArrayRef<Integer> indexs) { AvgValue1 = AverageFC(Close,FastLength); AvgValue2 = AverageFC(Close,SlowLength); //plt.line(\"MA1\",AvgValue1); //plt.line(\"MA2\",AvgValue2); Commentary(text(CurrentBar)); if(currentbar ==900) { Numeric i; For i=0 To 20 { x1Data[i]= Date[i]+Time[i]; y1Data[i]= AvgValue2[i]*1.01; } plt.line(\"vex0\",x1Data,y1Data); } if(currentbar ==898) { Numeric i; For i=0 To 20 { x1Data[i]= Date[i]+Time[i]; y1Data[i]= AvgValue2[i]*1.007; } plt.line(\"vex\",x1Data,y1Data); } if(currentbar ==899) { Numeric i; For i=0 To 20 { x1Data[i]= Date[i]+Time[i]; y1Data[i]= AvgValue2[i]*1.007; } plt.line(\"vex\",x1Data,y1Data); } if(currentbar ==900) { Numeric i; For i=0 To 20 { x1Data[i]= Date[i]+Time[i]; y1Data[i]= AvgValue2[i]*1.007; } plt.line(\"vex\",x1Data,y1Data); } if(currentbar == 901) { plt.clear(\"vex\"); } }