Logrithm bug? or I am just confused

[Fang]

hi,
sorry about raise another question, but i think it's related to SetMinMax question.

Set axis automatic to be false.

Code: Select all

        // axis automatic is false here
        // set all values to be position, just for testing
	for (int i=0; i<Series1->Count(); i++) {
		if (Series1->YValue[i]<=0) Series1->YValue[i]=1;
	}
        // change axis to logarithm.
	Chart1->LeftAxis->SetMinMax(1e-3,100);
	Chart1->LeftAxis->Logarithmic=true;

Correct me if any of the following is wrong. First of all, if automatic is false, the min and max is not updated so SetMinMax is required. But I got very confused here about Data Min(or Max) invisible and Axis Min (or Max) visible.

But SetMinMax has to be called before Logarithmic=true; and once set the axis can't be negative!! But the range of the axis shouldn't be the same of the data range, how do I set my range of axis to be (-1,100) while all of my data is actually all positive?

Thanks

[Fang]

I thought the following two lines should do the same thing, but the first one doesn't do anything for now if automatic is false.

Code: Select all

	Chart1->LeftAxis->AdjustMaxMin();
	Chart1->LeftAxis->SetMinMax(Series1->MinYValue(), Series1->MaxYValue()) ;

[Pep]

Hi Fang,

I'm sorry, I'm not sure which is the problem. Using the following code seems to work fine here :

Code: Select all

procedure TForm1.FormCreate(Sender: TObject);
var i:integer;
begin
   chart1.Axes.Left.Automatic:=false;
   // set all values to be position, just for testing
   for i:=0 to Series1.Count()-1 do
      if (Series1.YValue[i]<=0) then Series1.YValue[i]:=1;

   // change axis to logarithm.
   Chart1.Repaint;
   Chart1.LeftAxis.SetMinMax(1e-3,100);
   Series1.GetVertAxis.AdjustMaxMin;
   Chart1.LeftAxis.Logarithmic:=true;
end;

Could you please show me what should you get ?

[Fang]

I thought axis range can start from negtive while data is all positive. But obvious I am wrong, LOL.

Sorry about that.