How to get coordinates of the extreme points of a series ?

[bertrod]

Hello,

Is it possible to get the coordinates of the 2 points illustrated on the illustration below ? (With red circles around them).

[Narcís]

Hi bertrod,

Yes, you can do something like:

Code: Select all

procedure TForm1.FormCreate(Sender: TObject);
begin
  Series1.FillSampleValues();

  Chart1.Draw;
end;

procedure TForm1.Chart1AfterDraw(Sender: TObject);
var
  XVal,YVal: Double;
  XCoord, YCoord: Integer;
begin
  XVal:=Series1.XValue[0];
  YVal:=Series1.YValue[0];
  XCoord:=Series1.CalcXPos(0);
  YCoord:=Series1.CalcYPos(0);

  Chart1.Title.Text.Clear;
  Chart1.Title.Text.Add(FloatToStr(XVal)+', '+FloatToStr(YVal));
  Chart1.Title.Text.Add(IntToStr(XCoord)+', '+IntToStr(YCoord));

  XVal:=Series1.XValue[Series1.Count-1];
  YVal:=Series1.YValue[Series1.Count-1];
  XCoord:=Series1.CalcXPos(Series1.Count-1);
  YCoord:=Series1.CalcYPos(Series1.Count-1);

  Chart1.Title.Text.Add('');
  Chart1.Title.Text.Add(FloatToStr(XVal)+', '+FloatToStr(YVal));
  Chart1.Title.Text.Add(IntToStr(XCoord)+', '+IntToStr(YCoord));
end;

[bertrod]

Hello,

Thanks, but I had already thought about it and there is a "little problem" with your solution : when I zoom, the coordinates are not correct anymore because I need the extreme left and right points of the Series, but only with points which are shown on the screen .


For my problem, i tried to use the Series1.FirstValueIndex and Series1.LastValueIndex. But those values are not updated when zooming !

[Pep]

Hi,

in that case the only way around this would be to iterate through all the points after zoom checking if these are between the axis limits. Having this info you have to be able to get the corrdinate of the first and last visible valueindex.

[bertrod]

Ok, that's what I've done, and it works. Thanks.