AxisList[0].Range is not accepted
lazarus / 55-TAChart

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Firebird · 2022-02-03 10:44

Dear All,
I am using TAChart to generate a simple xy diagram (see image in the
attachment).
When I try to reset Chart1.AxisList[0].Range.Min or
Chart1.AxisList[0].Range.Max in the program the
application automatically changes it to the extension
of the y-axis of the graph presented. However, if I do this for
the Chart1.AxisList[1].Range.Min or Chart1.AxisList[1].Range.Max
it works fine. I have added the code of the form (the setting takes
place in function EditAxisScaling()), the corresponding Lazarus Form
and a screenshot of form at runtime. I would be very grateful for a
hint.

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wp · 2022-02-03 11:23

Sorry, I do not want to look at your code without compiler support -
it would be much more difficult. Please remove everything from the
form which is not needed and put it into a standalone project which I
can compile after you uploaded it under "Attachments and other
options". Put the .pas, .lfm, .lpr and .lpi files into a common zip
archive which is accepted by the forum software. Do not add any
compiler-generated files, otherwise the zip will become too large.

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Firebird · 2022-02-06 15:09

Thank you for the feedback. I have attached a miniproject with the
code as requested. Now, selecting the min and max values for the graph
display automatically focuses on the graph extensions on both axis
when min and max are selected (SpeedButton1 -> EditAxisScaling). It is
probably a configuration issue on my side - but which one? Thank you
for the help in advance.

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wp · 2022-02-06 15:40

There are several levels of priorities which affect the range of an
axis. The TChartAxis.Range has a very low priority. Next higher
priority is the range dictated by the series. This means that when the
data range covered by the series exceeds the range of the axis the
latter one is ignored.

The simplest way to achieve given axis limits is to assign them to the
Extent subproperties of the chart:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  
Chart.Extent.XMin := 0.7;  Chart.Extent.XMax := 1.1; 
Chart.Extent.YMin := 3.0;  Chart.Extent.YMax := 5.0; 
Chart.Extent.UseXMax := true;  Chart.Extent.UseXMin := true; 
Chart.Extent.UseYMax := true;  Chart.Extent.UseYMin := true;
But be carefull to apply the Use* in the correct order. The minimum
must never be greater than the maximum! To avoid this it is
recommended to use an auxiliary variable and let the chart apply the
limit at the same time in the FixTo method:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses 
TACharUtils;   // needed for TDoubleRect;...var  extent:
TDoubleRect;...  extent.a.x := 0.7;   // min x value  extent.b.x :=
1.1;   // max x value  extent.a.y := 3.0;   // min y value  extent.b.y
:= 5.0;   // max y value;  Chart1.Extent.FixTo(extent);

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Firebird · 2022-02-07 09:37

That really helped! Thank you very much, now everything is working as
it should.