用Chart画图，如何让系列2中有些缺少的值不显示？

我用Chart画图，有两个系列，其中一个系列数据多，画成直线图，第二个系列数据少，画成散点图。x坐标都是统一的坐标轴，想让系列2中缺少的值不显示。怎么办？
我的代码是这样的：

  Chart1.ChartAreas.Clear()
        Dim newChartAreas1 As New ChartArea("Default") 
        Chart1.ChartAreas.Add(newChartAreas1)
        Chart1.ChartAreas("Default").BackColor = Color.FromName("GradientInactiveCaption")
        Chart1.ChartAreas("Default").BackGradientStyle = GradientStyle.HorizontalCenter 
        Chart1.ChartAreas("Default").AxisX.IsMarginVisible = False
        Chart1.ChartAreas("Default").AxisX.Title = "DAY" 'X轴名称
        Chart1.ChartAreas("Default").AxisY.Title = "LAI" 'Y轴名称
        Chart1.ChartAreas("Default").AxisX.MajorGrid.LineDashStyle = ChartDashStyle.Dot
        Chart1.ChartAreas("Default").AxisY.MajorGrid.LineDashStyle = ChartDashStyle.Dot
        Chart1.ChartAreas("Default").AxisX.MajorGrid.LineColor = Color.Green
        Chart1.ChartAreas("Default").AxisX.MajorTickMark.Interval = 10
        Chart1.ChartAreas("Default").AxisX.MajorTickMark.Enabled = True
        ' Chart1.ChartAreas("Default").AxisX.IsMarginVisible = False
        Chart1.ChartAreas("Default").AxisY.IsMarginVisible = True
        Chart1.ChartAreas("Default").AxisX.LineWidth = 0
        'Chart1.ChartAreas("Default").AxisX.Interval = 15
        Chart1.ChartAreas("Default").AxisY.Interval = 2
        Chart1.ChartAreas("Default").AxisX.MajorGrid.Interval = 1000
        Chart1.ChartAreas("Default").AxisY.MajorGrid.Interval = 1000

        Chart1.Titles.Clear()
        Dim newTitles1 As New Title("LAI Simulation") '建立标题
        newTitles1.Text = "LAI Simulation"
        Chart1.Titles.Add(newTitles1)

        Chart1.Series.Clear() '清除所有数据集
        Dim newSeries1 As New Series("LAI") '新增数据集
        newSeries1.ChartType = SeriesChartType.Line       '直线
        newSeries1.BorderWidth = 2
        newSeries1.Color = Color.Red
        '  newSeries1.XValueType = ChartValueType.Date
        '   newSeries1.IsValueShownAsLabel = False
        newSeries1.IsValueShownAsLabel = False
        newSeries1.IsVisibleInLegend = True
        newSeries1.MarkerStyle = MarkerStyle.Diamond
        newSeries1.MarkerStep = 10
        Chart1.Series.Add(newSeries1)


        For i = 0 To out_n - 1
            Chart1.Series("LAI ").Points.AddXY(i, out_lai(i))

        Next


        Dim newSeries2 As New Series("LAI 2") 
        newSeries2.ChartType = SeriesChartType.Point     
        newSeries2.BorderWidth = 2
        newSeries2.Color = Color.Blue
        newSeries2.IsValueShownAsLabel = False
        newSeries2.MarkerStyle = MarkerStyle.Diamond
        Chart1.Series.Add(newSeries2)
        For i = 20 To out_n - 1
            Chart1.Series("LAI 2").Points.AddY(out_lai(i))
        Next