Steema Central

Posted: **Wed Apr 06, 2022 7:37 pm**

Hi
I generate some graphs with elliptical boundaries around data points (see attachment with magenta ellipses). These ellipses represent, say, 1 sigma uncertainties for individual data points. I would like to be able to colour the interior of each ellipse, with variable opacity and maybe gradient according to values in some other variable in a dataset.

Please could you advise me whether there is currently any option in TeeChart to fill inside some calculated/defined boundary (like the ellipses in the attached image) and whether it would also be possible to colour according to a third data variable?

Any advice for how to achieve this (if possible with current versions of TeeChart) would be much appreciated.

Thanks
Bruce

: Example Concordia plot.jpg (217.11 KiB) Viewed 10776 times

Posted: **Fri Apr 08, 2022 2:56 pm**

Hello Bruce,

You could take the point values that you use to plot the data, converting them to pixel locations using:

Series1.CalcXPosValue(value) and Series1.CalcYPosValue(value)

..or loop through the indexes of the points using:

Series1.CalcXPos(idx) and Series1.CalcYPos(idx)

..and adding them to an array of TPoints. You can then plot the array in the OnAfterDraw event using:

Code: Select all

Chart1.Canvas.Polygon(yourArray);

Before you plot the polygon, set the Brush to fill as you require.

eg.

Code: Select all

  Chart1.Canvas.Brush.Gradient.StartColor := clRed;  //can use (a)rgb colours
  Chart1.Canvas.Brush.Gradient.EndColor := clYellow;
  Chart1.Canvas.Brush.Gradient.Visible := True;

  Chart1.Canvas.Polygon(yourArray);

Regards,
Marc Meumann

Posted: **Tue Apr 12, 2022 8:59 pm**

Thanks. I am missing something though and am not sure what the associations are.

What is the array definition meant to be? is it something like

Code: Select all

MyArray : array of TPoint;

or should this be TPoints, in which case TPoints must be defined in some unit I am not aware of.

When adding the pixel location data to the array, I presume that this should be something like

Code: Select all

for i := 1 to N   // N is count for existing Series dataset
  MyArray[i].Create(Xloc,Yloc);
end;

but this does not seem to work.

Any help would be much appreciated

Thanks
Bruce

Posted: **Tue Apr 19, 2022 8:10 am**

Hello Bruce,

This example would go some way to the goal, proof of concept. You can make adjustments as necessary:

Code: Select all

procedure TForm1.Chart1AfterDraw(Sender: TObject);
var i : Integer;
    myPoints : Array of TPoint;
begin
  Chart1.Canvas.Brush.Gradient.StartColor := clRed;  //can use (a)rgb colours
  Chart1.Canvas.Brush.Gradient.EndColor := clYellow;
  Chart1.Canvas.Brush.Gradient.Visible := True;

  SetLength(myPoints, Series1.Count);
  for i:= 0 to Series1.Count-1 do
  Begin
    myPoints[i] := TPoint.Create(Series1.CalcXPos(i),Series1.CalcYPos(i));
  End;

  Chart1.Canvas.Polygon(myPoints);
end;

Regards,
Marc

Steema Central

Filling within outlines on graphs

Filling within outlines on graphs

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Re: Filling within outlines on graphs

Re: Filling within outlines on graphs