Show Last X samples in Graph
lazarus / 55-TAChart

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Bas · 2020-06-19 07:55

In a graph i show realtime data which is coming in at 100Hz so the
graph fills up very quickly. Is it possible to show only the last 1000
or 10000 samples with the graph shifting automaticly  ?

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wp · 2020-06-19 08:20

What should happen with the older values? Should they be deleted so
that the series contains never more then, say, 1000 points? Or should
they still be stored but the visible window should be decreases so
that only the last 1000 points are visible although there are more
points in the series? In the latter case, should it be possible to
scroll back to previous data points, or should there be a need to see
all points?

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Bas · 2020-06-19 08:29

Older points can just be disregarded/deleted

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wp · 2020-06-19 08:45

Play with the attached demo.

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Bas · 2020-06-19 10:56

That works fine but due to the moving grid in the backgroud it looks
like crap   . Is there a way to switch off the x-axis on the grid in
the background ?

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wp · 2020-06-19 11:30

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
Chart1.BottomAxis.grid.Visible := false;    // Hide the x axis
gridChart1.BottomAxis.Marks.visible := false;   // Hide the x axis
labels and ticks
You may also want to keep the x axis at a constant scaling factor to
avoid the expansion while the first data points are added. Put this
code into the routine which receives the data, in my example in the
OnTimer event handler:

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  
Chart1.BottomAxis.Range.Max := t;  Chart1.BottomAxis.Range.Min := t -
MAX_POINTS * Timer1.Interval/1000;  Chart1.BottomAxis.Range.UseMax :=
true;  Chart1.BottomAxis.Range.UseMin := true;

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Bas · 2020-06-22 04:14

Thx, works all perfect now