The following project shows you how to use classes of the chart component gb.chart to create a line symbol chart → Figure 23.8.1.1 SWR line chart:

Figure 23.8.1.1: SWR line-symbol diagram

This is the complete, sufficiently commented source code:

' Gambas class file
 
Public hChart As New Chart
 
Public Sub Form_Open()
 
    FChart.Resizable = True
 
'-- Creates a diagram with the given properties and data.
    CreateChart()
 
End
 
Public Sub CreateChart()
 
    SetChartGeneral()
    SetChartType()
    SetChartColors()
    SetChartLegend()
    SetChartXAxis()
    SetChartYAxis()
    SetChartValues()
 
End
 
Public Sub DrawingArea1_Draw()
 
'-- Sets the height and width of the diagram.
    hChart.Width = DrawingArea1.ClientWidth
    hChart.Height = DrawingArea1.ClientHeight
 
'-- The chart object can be rendered on a form in a DrawingArea.
    hChart.Draw()
 
End
 
Public Sub Form_Close()
 
    FChart.Close()
 
End
 
'-- Private Procedure ------------------------------------------------------------------ 
 
Private Sub SetChartGeneral()
 
'-- Sets the color for the background of the diagram
    hChart.BackGround = Color.White ' &HC3DDFF
 
'-- Sets a border around the diagram
    hChart.Border = True
 
'-- Sets the diagram description (titel)
    hChart.Title.Visible = True
    hChart.Title.Text = ("SWR frequency diagrams for different antennas")
    hChart.Title.Font = Font["NotoSans,24"] ' Font for the title - absolute in px
 
'-- Sets the diagram style
    hChart.Style = ChartStyle.Default
    hChart.Proportionnal = True
 
End
 
Private Sub SetChartColors()
 
'-- Sets the user-defined colors
    hChart.Colors.Style = Chart.Colors.Custom
    hChart.Colors.Values = [Color.Red, Color.Blue, Color.Green]
 
'-- Alternative: Sets the colors automatically
'   Chart.Colors.Style = Chart.Colors.Auto
 
End
 
Private Sub SetChartType()
 
'-- Sets the diagram type
    hChart.Type = ChartType.LinesSymbols
 
End
 
Private Sub SetChartValues()
 
    Dim hDBResult As Result
    Dim i As Integer
 
'-- Sets the number of data series.
    hChart.CountDataSets = 3
 
'-- Returns the result of a database query as a database result
    hDBResult = DBCS.DBConnection.Exec("SELECT frequenz, fb3320, yagi20, loop20 FROM " & "testseries1")
 
'-- Sets the values on the X-axis as a character string for each data series!
    For i = 1 To hDBResult.Count
 
      hDBResult.MoveTo(i - 1)
 
  '-- Sets the x-values in a string array
      hChart.Headers.Values.Add(CStr(hDBResult!frequenz))
 
  '-- Sets the y-values as float values
      hChart[0].Values.Add(hDBResult!fb3320)
  '-- Text to display in the legend
      hChart[0].Text = "FB33"
 
      hChart[1].Values.Add(hDBResult!yagi20)
  '-- Text to display in the legend
      hChart[1].Text = "2-Element-Monoband-Yagi"
 
      hChart[2].Values.Add(hDBResult!loop20)
  '-- Text to display in the legend
      hChart[2].Text = "2-Element-Monoband-Loop"
    Next
 
End
 
Private Sub SetChartLegend()
 
    hChart.Legend.Visible = True
    hChart.Legend.Position = Align.Bottom 	' Position either .Bottom or .Right
    hChart.Legend.Font = Font["NotoSans,14"] 	' Font for the title - absolute in px
    hChart.Legend.Title = ("Antenna type:")
 
End
 
Private Sub SetChartXAxis()
 
'-- X-Axis
    hChart.XAxe.Visible = True
    hChart.XAxe.MinValue = 14.00
    hChart.XAxe.MaxValue = 14.40
    hChart.XAxe.Step = 0.25
 
End
 
Private Sub SetChartYAxis(Optional argAuto As String)
 
'-- Y-Axis
    hChart.YAxe.Visible = True
    hChart.YAxe.ShowIntervalLines = True
 
    If argAuto And If Lower(argAuto) = "auto" Then
       hChart.XAxe.AutoScale = True
    Else
       hChart.YAxe.MinValue = 1
       hChart.YAxe.MaxValue = 3.25
       hChart.YAxe.Step = 0.25
    Endif
 
End

Notes:

The gb.chart component must be integrated into the project and the data to be displayed comes from an SQLite database table. The database is included in the project:

Figure 23.8.1.2: Database table (frequency and SWR)

There is no option in the gb.chart component to

• to additionally draw the direction arrows of the coordinate axes,
• to insert the identifier of the x-axis (abscissa) or
• insert the identifier of the y-axis (ordinate).