[Solved] I set VertAxis.Range.Min:=0 and UseMax:=true but still see data below 0

[dvhx]

I'm using TChart. My data y is from 0 to 5 but I want to see y axis from 0, to 10, so I use this Min:=0, Max=10, UseMin:=true, UsaMax:=true. This works, but if I have data that goes below zero, chart ignores Min:=0,UseMin:=true and increases y axis range to -1 fit the chart on screen. I don't want to modify data, I just want initial view to be from 0 to 10, not from -1 to 10.

Code: Pascal  [Select][+][-]

1. var s : TLineSeries;
2. begin
3.   s := TLineSeries.Create(Chart1);
4.   s.AddXY(0,0);
5.   s.AddXY(1,5);
6.   s.AddXY(2,0);
7.   s.AddXY(3,5);
8.   s.AddXY(4,0);
9.   s.AddXY(4.1,-1); // random noise in data I'm not interested in
10.   s.AddXY(4.2,0);
11.   s.AddXY(5,5);
12.   s.AddXY(6,0);
13.   Chart1.AddSeries(s);
14.   Chart1.VertAxis.Range.Min := 0;
15.   Chart1.VertAxis.Range.Max := 10;
16.   Chart1.VertAxis.Range.UseMax := true;
17.   Chart1.VertAxis.Range.UseMin := true;
18. end;
19.  

Lazarus 2.2.0+dfsg1-5ubuntu1 (rev Unversioned directory) FPC 3.2.2 x86_64-linux-gtk2 Ubuntu 22.04.5 LTS

[wp]

Use the Chart.Extent to freeze the axis limits.

Code: Pascal  [Select][+][-]

1. Chart.Extent.YMin := 0;
2. Chart.Extent.YMax := 10
3. Chart.Extent.UseYMin := true;
4. Chart.Extent.UseYMax := true;

But note that the Chart.Extent is given in "graph coordinates" (see https://wiki.lazarus.freepascal.org/TAChart_documentation#Coordinates_and_axes for an explanation), so when you have a logarithmic axis and want it to range between 0.1 and 1000 you must set Chart.Extent.YMin = -1 and Chart.Extent.YMax = 3 (these are the logarithms of 0.1 and 1000, respectively).

[dvhx]

This solved it, thanks