Steema Central

Posted: **Mon Jul 16, 2007 10:04 am**

Hi !

We have a logging software which plots every second one point to the chart / to the series (we use fastline Series).
Everytime a new point is added to a series the chart is repainted. So the increment of the x axis is only one point.
Is there a way to increment the x axis with a custom percentage?

A simple example:
Lets say you have one FastLine Series with 100 datapoints. The X axis shows 0 at the left and 100 at the right. Now you add an addition datapoint to the series. The x axis only increments to 101 on the right side.
But it would be much more efficient if the x axis would increment to 120 instead of 101. If you do so the next 19 datapoints don´t need a complete repaint of the chart. You simple enhance the actual one.
If you have 120 datapoints you enhance the x axis again with 20%.

Is this possible with TeeChart?

Posted: **Mon Jul 16, 2007 10:10 am**

Hi Dominik,

this can be accomplished using the SetMinMax method, it will allow you to specify the min and max for the bottom axis after the point has been added.

Posted: **Mon Jul 16, 2007 10:17 am**

Hi Pep,

thx !

But there is no automatism which will do this?

Posted: **Mon Jul 16, 2007 12:07 pm**

Hi Pep,

I write some code in FormCreate:

Code: Select all

  Series1.GetHorizAxis.Automatic := False;
  Series1.GetHorizAxis.SetMinMax(0, 10);

Then I add datapoints with a timer:

Code: Select all

procedure TForm1.Timer1Timer(Sender: TObject);
var NewMax : Double;
begin
  inc(Count);

  if Count > Series1.GetHorizAxis.Maximum then begin
    NewMax := round(Chart1.Series[0].Count * 1.2);
    Series1.GetHorizAxis.SetMinMax(0, NewMax);
  end;

  Chart1.Series[0].AddXY(Count, Sin(Count / 30));
  Chart1.Series[1].AddXY(Count, Cos(Count / 30));
end;

The x Axis increments great

But I don´t understand why the chart is repainted every time a new datapoint is added. In the OnAfterDraw Event I put in some Debugcode and it is fired every time you add a datapoint.

Wouldn´t it be much faster if the chart will only be redrawn if the axis have to be recalculated?

Posted: **Fri Jul 27, 2007 7:58 am**

Hi Dominik,

The most usual wish is to show each new point added to a series. I don't understand what exactly you would like to achieve.

You would like to control OnAfterDraw calls? You can control chart repaints by:

Code: Select all

Chart1.AutoRepaint := False;

If what you want is to add some values in one time you can use the AddArray method:

Code: Select all

Series1.AddArray([2,3,5,7,1]);

Steema Central

Increment of x Axis

Increment of x Axis