Tutorial 4 - Axis Control

TeeChart Pro will automatically define all Axis labelling for you and offers plenty of flexibility to tailor any specific requirements you may have. TeeChart Pro offers true Multiple Axes. These are available at design or run time and offer countless possibilities and flexibility for Axis definition. See the section in this tutorial for more information.

Contents

Axes control - Key areas

Scales

Axis scales are set automatically when you add Series data to your Chart. You may change from the defaults at design time or at runtime by using Axis properties.

	Non date-time data When adding a new Series, the Scales section of the Axis Page of the Chart Editor will show Automatic selected and other options greyed out. All values shown are numeric.
	Date-time data When a Series has datetime set to true (for that axis) on the Series, General page, the Scales section of the Axis Page of the Chart Editor will show Automatic selected and other options greyed out. Values are shown with Date-time values.

Automatic selects the best axis scale range to fit your data. If you turn Automatic off the scales section will ungrey options and you can change Axis values. Important, remember to select the Axis that you wish to configure from the list of Axes on the left of the page.

Add a Line Series to a Chart add a Command Button with the following code:

Dim t As Integer
For t = 0 To 40
  With TChart1.Series(0)
    .Add CInt((Rnd) * t), "", vbRed
  End With
Next t

Running the code in the button will draw a Line Series with 40 random values. Go to the Chart Editor at design time. Turn Automatic 'off' in the Bottom Axis scales section of the Axis page. You may now configure Maximum and minimum values for the Axis scale. Running the code again will show values depending on the values you configured for the Axis. Using the right button of of the mouse you may scroll to see the remaining values.

Setting axis scales by code
You can change the Maximum and Minimum at runtime using this code:

With TChart1.Axis.Bottom
  .Automatic = False
  .Maximum = 36
  .Minimum = 5
End With

You may set Axis scale Maximum and Minimum to automatic individually. e.g:

With TChart1.Axis.Bottom
  .AutomaticMaximum = True
  .AutomaticMinimum = False
  .Minimum = 5
End With

Offset
You may set Axes to have Offsets (in pixels) for both Minimum and Maximum scales.

TChart1.Axis.Left.MaximumOffset = 4
TChart1.Axis.Left.MinimumOffset = 4

Increment

You may tailor the intervals for the Axis. Select the Desired Increment combobox from the Scales section of the Axis page and add the increment you require. You may change this by code at runtime:

With TChart1.Axis.Bottom
  .Increment = 20
End With

Datetime data

If your data is datetime (You may set the data to datetime for your Series by going to the Series, General page), the Chart, Axis page, scales section will show datetime range. Select the increment from the range shown in the Desired Increment combobox.
add some sample data

For t = 1 To 25
   With TChart1.Series(0)
       .AddXY DateValue("2017, 11, " & t), Rnd(t) * t, "", vbRed
   End With
Next t

Change the Increment at runtime:

With TChart1.Axis.Bottom
  .Increment = TChart1.GetDateTimeStep(dtTwoDays)
End With

See the Axis.ExactDateTime property for more information about date axis labelling

Note

When changing axis label frequency, bear in mind that TeeChart will avoid label overlap according to the setting of the LabelsSeparation property. This means that if the label frequency is too high for the labels to fit, then TeeChart will allocate 'best fit'. Changing the label angle and label separation are 2 options that may help you fit the labels you require. See the Labels section and LabelsAngle property.

Titles

Titles are set in the Titles section of the Axis page. You may change the Title text for the Axis and its font. The angle may be selected from values 0, 90, 180, 270 degrees. For runtime see Axis Title Class.

Labels

See the AxisLabels Class (IAxislabels interface) for a resume of Labels properties.

Note

When changing axis label frequency, bear in mind that TeeChart will avoid label overlap according to the setting of the Labels.separation property. This means that if the label frequency is too high for the labels to fit, then TeeChart will allocate 'best fit'. Changing the label angle and label separation are 2 options that may help you fit the labels you require. See the Labels.Angle property.

Label formats
You may apply all standard number and date formats to Axis labels. The Axis page, Labels section contains the field "Values format". If your data is datetime the field name changes to "Date time format". In the Editor drag the help "?" icon onto the field to get a full listing of options. At runtime use:

With TChart1.Axis.Bottom
  .Labels.ValueFormat = "#,##0.00;(#,##0.00)" 
End With

'or for datetime data

With TChart1.Axis.Bottom
  .Labels.DateTimeFormat = "dd/mmm/yy" 'Datetime
End With

MultiLine labels
Axis labels can be displayed as multi-line text instead of a single line of text. Lines are separated using the carriage-return ascii character ( #13 ).

Example

//Add the Series labels in this way and apply 'Marks' as Axis labelling style
  TChart1.Series(0).Add 1234, "New"+chr$(13)+"cars", vbRed
  TChart1.Series(0).Add 2000, "Old"+chr$(13)+"bicycles", vbBlue

Example for DateTime labels:

The following will show the Bottom Axis labels in two lines of text, one showing the month and day, and the second line showing the year:
Feb-28 Mar-1 .. 1999 1999 ..

TChart1.Series(0).AddXY DateValue("28,2,1999"), 100, "", clTeeColor
TChart1.Series(0).AddXY DateValue("1,3,1999"), 200, "", clTeeColor
TChart1.Series(0).AddXY DateValue("2,3,1999"), 150, "", clTeeColor
TChart1.Series(0).XValues.DateTime = True
TChart1.Axis.Bottom.Labels.DateTimeFormat = "mm/dd hh:mm" 'space

If you set the Labels.MultiLine property to True, the axis will automatically split labels in lines where it finds a space.

TChart1.Axis.Bottom.Labels.MultiLine = True

Dividing the Label into two:

'mm/dd' for the first line
'hh:mm' for the second line

At run-time you can always split the label into lines programatically, using the OnGetAxisLabel event:

Private Sub TChart1_OnAfterDraw()
  TChart1.Axis.Left.Labels.TeeSplitInLines LabelText, " "
End Sub

The global "TeeSplitInLines" procedure converts all spaces in "LabelText" to line separators (returns).

The axis Labels.Angle property ( label rotation in degree angles 0, 90, 180 or 270 ), can also be used with multi-line axis labels.

Customising Axis labels
Further Label control may be obtained by using Axis events. The events permit you to activate/deactivate/change any individual Axis label. The following example modifies each Label, putting a textual phrase in front of the point index value.

'set LabelStyle to 'Mark' with the TChart editor or use:-
TChart1.Axis.Bottom.Labels.Style = talMark

'OnGetaxisLabel event
Private Sub TChart1_OnGetAxisLabel(ByVal aAxis As Long, ByVal SeriesIndex As Long, ByVal ValueIndex As Long, LabelText As String)
 If aAxis = atBottom Then
   LabelText = "Period " + Str(ValueIndex)
 End If
End Sub

See the section entitled Axis events for more information about customising labels with Axis events.

Axes labels may be modified at specific positions with custom text and formatting without the need to use TeeChart events, making them much easier to modify serverside in ASP scenarios.

Private Sub Form_Load()
Dim v As Variant
  v = Array(200, 0, 123, 300, 260, -100, 650, 400)
  TChart1.AddSeries scLine
  TChart1.Series(0).AddArray 8, v
  AddCustomLabels
End Sub

Private Sub AddCustomLabels()
  TChart1.Axis.Left.Labels.Clear
  TChart1.Axis.Left.Labels.Add 123, "Hello"
  TChart1.Axis.Left.Labels.Item(0).Font.Size = 16
    
  TChart1.Axis.Left.Labels.Add 466, "Good" & Chr(13) & "Bye"
  TChart1.Axis.Left.Labels.Item(1).Transparent = False

  TChart1.Axis.Left.Labels.Add 300, ""
  
  TChart1.Axis.Left.Labels.Add -100, ""
  With TChart1.Axis.Left.Labels.Item(3)
    .Transparent = False
    .Transparency = 50
    .Color = vbBlue
  End With
End Sub

Logarithmic Labels
Normal Logarithmic labelling may be set in the following way:

With TChart1.Axis.Left
 .Logarithmic = True
 .Increment = 0 ' the default
 .SetMinMax 0, 10000
 .Labels.ValueFormat = "#e+0" ' exponential format
End With

Labels will be set according to the Logarithmic base (default 10) thus, in this case giving labels at 1,10,100,1000,10000.

Ticks and Minor

There are 3 tick types and 2 types of Grid. You may change the length, width and colour of each tick and Grid type. Changes can be made to Ticks, their associated Grid and Inner Ticks via the «Ticks» tab; changes to Minor Ticks and their associated Grid can be made via the «Minor» tab.

With TChart1.Axis.Bottom
  .TickLength = 7
  .Ticks.Color = vbGreen
  .MinorTickCount = 10 'change number of minorticks between (major) Ticks
End With

Axis position

Axes have a property to modify where each axis is to be located. In this example, the axis is moved 50% of the total Chart width, so it is shown at the chart center:

TChart1.Axis.Left.PositionPercent = 50

Additional Axes

Copying axes

TeeChart offers 5 axes to be associated with data Series, Left, Top, Bottom, Right and Depth. When you add a new series to a Chart you may define to which of the axes the Series should be related (Go to the Series tab, General page). You may repeat anyone (or all) of the front 4 axes at any place on the Chart by using the Axis Customdraw method. Note that this method makes a copy of your Axis, it does not add a new Custom Axis. See the next section, Multiple Custom Axes, for more information.

Example:

'fill the Series for this example with random data
Private Sub Command1_Click()
Dim t As Integer
  For t = 0 To 20
    TChart1.Series(0).AddXY t, ((100 * Rnd) + 1) - ((Rnd * 70) + 1), "", vbRed
  Next t
End Sub

'Put this code in the TChart1_OnBeforeDrawSeries() event:
Dim posaxis As Integer
  With TChart1
   If .Axis.Left.Maximum > 0 Then
    'When scrolling or on zoom always keep the gridlines enclosed in the Chart rectangle
    .Canvas.ClipRectangle .Canvas.Left, .Canvas.Top, (.Canvas.Left + .Canvas.Width), _
                          (.Canvas.Top + .Canvas.Height)
    'Always draw the 2nd vertical Axis at the middle point of the Chart
    posaxis = (.Canvas.Left) + (.Canvas.Width * 0.5)
    .Axis.Left.CustomDraw posaxis - 10, posaxis - 20, posaxis, True
    'Draw the 2nd Horizontal axis at the level of "10" on the vertical axis
    posaxis = (.Axis.Left.CalcYPosValue(10))
    .Axis.Bottom.CustomDraw posaxis + 10, posaxis + 40, posaxis, True
    .Canvas.UnClipRectangle
   End If
  End With

Custom axes

In this example, TeeChart will plot the New axes, one horizontal and one vertical in the centre of your Chart. When you scroll the Chart (dragging with right mouse button), the new vertical axis will always remain central to the Chart, the new horizontal axis will move up and down with vertical scrolling. The new axes are exact copies of the default axes.

Multiple Custom Axes

Together with the PositionPercent and stretching properties, it’s possible to have unlimited axes floating anywhere on the chart. Scroll, zoom, and axis hit-detection also apply to custom-created axes. Creating extra axes is now possible both at designtime via the Chart Editor and at runtime via a few lines of code:

Via the Chart Editor

TeeChart offers you the ability to create custom axes at designtime enabling them to be saved in TeeChart's tee file format. To achieve this, open the Chart Editor and click on the Axis tab and then select the "+" button to add a Custom Axis. Then select the Position tab making sure you have your new Custom Axis highlighted. The Horizontal checkbox on this page allows you to define your new Custom Axis as an horizontal axis or to leave it as the default vertical axis. The rest of this page and the other tabs in the Axis page can be used to change the Scales, Increment, Titles, Labels, Ticks, Minor Ticks and Position of the Custom Axis as explained above. To associate this new Custom Axis with the Data Series you desire select the Series tab and go to the General page where the dropdown Comboboxes 'Horizontal Axis' and 'Vertical Axis' will enable you to select your new Custom Axis depending on whether you previously defined it as vertical or horizontal.

Via Code

Example

Private Sub Command1_Click()
TChart1.Series(0).VerticalAxisCustom = TChart1.Axis.AddCustom(False)
'You can modify any property of the new created axes, such as the axis color or axis title
With TChart1.Axis.Custom(0)
    .AxisPen.Color = vbGreen
    .Title.Caption = "Extra axis"
    .Title.Font.Bold = True
    .Title.Angle = 90
    .PositionPercent = 50 'percentage of Chart rectangle
End With
End Sub

You are able to then position the new Axis in overall relation to the Chart by using the StartPosition and EndPosition properties.

StartPosition=50
EndPosition=100

These figures are expressed as percentages of the Chart Rectangle with 0 (zero) (in the case of a vertical Axis) being Top. These properties can be applied to the Standard Axes to create completely partitioned 'SubCharts' within the Chart.

Example

With TChart1.Axis.Left
    .StartPosition = 0
    .EndPosition = 50
    .Title.Caption = "1st Left Axis"
    .Title.Font.Bold = True
End With

The above 2 coded examples when combined with the following data:

For t = 0 To 10
    TChart1.Series(0).AddXY t, 10 + t, "", clTeeColor
    If t > 1 Then
      TChart1.Series(1).AddXY t, t / 2, "", clTeeColor
    End If
Next t

...will show the following Chart:

Multiple axes

Options are limitless! We advise caution when using Custom Axes as it is easy to start filling the screen with new axes and to lose track of which one you wish to manage !

Axis events

Axis events offer runtime flexibility to modify Axis Labels and present user interactivity on Axis Clicks.

OnClickAxis

See the OnClickAxis event.

Example

Private Sub TChart1_OnClickAxis(ByVal Axis As Long, ByVal Button As TeeChart.EMouseButton, ByVal Shift As TeeChart.EShiftState, ByVal X As Long, ByVal Y As Long)
'Shows Axis point clicked when click on Bottom Axis.
If Axis = atBottom Then
  MsgBox "Clicked Bottom Axis at " & TChart1.Axis.Bottom.CalcPosPoint(X)
End If
End Sub

OnGetAxisLabel

Can be used to modify Axis Labels. See the OnGetAxisLabel event.

Example

Private Sub TChart1_OnGetAxisLabel(ByVal aAxis As Long, ByVal SeriesIndex As Long, ByVal ValueIndex As Long, LabelText As String)
'Add following text to Bottom Axis Labels
If aAxis = atBottom Then
  LabelText = "Period " + LabelText
End If
End Sub

OnGetNextAxisLabel

Can be used to decide which Axis Labels should be displayed. See the OnGetNextAxisLabel event. You should use the MoreLabels Boolean property to include/exclude Axis Labels.

Example

Private Sub TChart1_OnGetNextAxisLabel(ByVal Axis As Long, ByVal LabelIndex As Long, LabelValue As Double, MoreLabels As Boolean)
If Axis = atBottom Then
   MoreLabels = True
   'Only label if following cases are true
   Select Case LabelIndex
      Case 0: LabelValue = 11
      Case 1: LabelValue = 19
      Case 2: LabelValue = 23
      Case Else: MoreLabels = False
   End Select
End If
End Sub