C# と VB.NET の質問掲示板

■No86436 (mako さん) に返信


若干違うかもしれませんが
以下のようにNullの要素を追加するとそこだけデータがプロットされません。
時間の項目に文字列を使うのはグラフ上扱いにくいのでグラフ用のDataTableを
用意されて時間項目はDateTime型にされた方がよいです。
DataTable１つの場合はDataSetを使う必要はなくDataTable直接でよいです。

        _tbl = New DataTable()
        With _tbl.Columns
            .Add("t", GetType(DateTime))
            .Add("y1", GetType(Integer))
            .Add("y2", GetType(Integer))
        End With

        With _tbl.Rows
            .Add(Date.Today.AddHours(8).AddMinutes(45), 30, 2)
            .Add(Date.Today.AddHours(9).AddMinutes(0), 20, 3)
            .Add(Date.Today.AddHours(9).AddMinutes(15), 20, 3)
            .Add(Date.Today.AddHours(9).AddMinutes(30), 5, 4)
            .Add(Date.Today.AddHours(9).AddMinutes(45), 10, 8)
            .Add(Date.Today.AddHours(10).AddMinutes(0), 15, 10)
            .Add(Date.Today.AddHours(10).AddMinutes(15), DBNull.Value, DBNull.Value)
            .Add(Date.Today.AddHours(10).AddMinutes(30), DBNull.Value, DBNull.Value)
            .Add(Date.Today.AddHours(11).AddMinutes(15), 5, 3)
            .Add(Date.Today.AddHours(11).AddMinutes(30), 20, 15)
            .Add(Date.Today.AddHours(11).AddMinutes(45), 5, 3)
            .Add(Date.Today.AddHours(12).AddMinutes(0), 10, 8)
            .Add(Date.Today.AddHours(12).AddMinutes(15), 20, 10)
        End With

        Chart1.DataSource = _tbl
        With Chart1.ChartAreas(0)
            With .AxisX
                .Minimum = Date.Today.AddHours(8).AddMinutes(45).ToOADate
                .Maximum = Date.Today.AddHours(12).AddMinutes(15).ToOADate
                .IntervalType = DataVisualization.Charting.DateTimeIntervalType.Minutes
                .Interval = 30


                Dim isFirst = True
                For Each row In _tbl.Select("", "t")
                    Dim dt = row.Field(Of Date)("t")
                    If isFirst OrElse dt.Minute = 0 OrElse dt.Minute = 30 Then
                        With .CustomLabels.Add(dt.AddMinutes(-3).ToOADate, dt.AddMinutes(3).ToOADate, dt.ToString("HH:mm"))
                            .RowIndex = 0
                        End With
                    End If
                    isFirst = False
                Next


            End With
        End With
        With Chart1.Series(0)
            .XValueMember = "t"
            .YValueMembers = "y1"
        End With
        With Chart1.Series.Add("")
            .ChartType = SeriesChartType.Line
            .EmptyPointStyle.Color = Color.Transparent
            .XValueMember = "t"
            .YValueMembers = "y2"
        End With