Reduce the number of drawn TChart points

Question

My TChart has a lot of points added by series.AddXY method. A point is added every second (but there could be also long periods without data). After the chart has been changed (point added), when I go to the tab with the chart, it takes about 5 seconds before it is repainted.

I thought that using an aggregate function would help to draw the chart faster:

ser1: TFastLineSeries;
ser2: TPointSeries;
ser3: TFastLineSeries;
utc: TDateTime;

ser1.SetFunction(TAverageTeeFunction.Create(Self));
ser1.FunctionType.Period := 100;
ser1.FunctionType.PeriodStyle := psRange;

ser2.SetFunction(TAverageTeeFunction.Create(Self));
ser2.FunctionType.Period := 100;
ser2.FunctionType.PeriodStyle := psRange;

ser3.SetFunction(TAverageTeeFunction.Create(Self));
ser3.FunctionType.Period := 100;
ser3.FunctionType.PeriodStyle := psRange;

for i := 0 to 30000 do begin
   .....
   ser1.AddXY(utc, 0, utcStr);
   ser2.AddXY(utc, deviation, utcStr);
   ser3.AddXY(utc, trend, utcStr);
   .....
end;

but it is as slow as it was.

How to draw the chart faster?

Update

This is non-zoomable chart for 3 hours of data. "Now" is at the right edge, "-3h" on the left. Points are constantly arriving to the right and deleted from the left. The view frame is shifted by setting chart.BottomAxis.Minimum and chart.BottomAxis.Maximum properties. I would be satisfied by AVG drawing where amount of averages is the horizontal amount of pixels on the chart.

https://stackoverflow.com/questions/4767684/large-tchart-takes-a-long-time-to-draw Also consider some kind of decimation if possible — MBo, Jun 25 '18 at 09:37
For oscillograph-like charts I prepared data arrays (at most 1024 points) and fill them with filtered data, then renewed last value and refill Series data at every step — MBo, Jun 25 '18 at 11:01
Do you still need the data to the left of chart.BottomAxis.Minimum? If not, you might want to delete these points once in a while which would free up memory and might also improve drawing performance a bit. — dummzeuch, Jun 25 '18 at 12:11
@dummzeuch: If I wouldn't do this, the chart will get stuck completely. — Paul, Jun 25 '18 at 13:48

Paul · Accepted Answer · 2018-06-25T14:39:34.927

1

I rounded DateTime value

axisTimestamp := Trunc(timestamp * 40000) / 40000;

and then used this value to set chart point.

If a point with such XValue exists then I calculate an average:

if series.XValue[i] = axisTimestamp then
    series.YValue[i] := (series.YValue[i] + newValue) / 2;

edited Jun 25 '18 at 14:39

answered Jun 25 '18 at 13:47

Paul

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Reduce the number of drawn TChart points

1 Answers1