Real-time data performance

[smofe]

I have a project were I need to render multiple charts of incoming sensor data. The charts should be updated at least every 30ms and show up to 1000 data points at a time, as a line chart. Is this library suited for this use-case and capable of this performance?

Thanks for any tips.

[entronad]

I think it is suite for your case. There are some optimizations for fast updating in this lib.

I believe your updating is triggered by setState in the widget tree, make sure to set rebuild: false, and changeData: true if the data is modified in the same list instance, then each time the widget updates, the chart will not rebuild the whole operators flow but only pulse data related operators and update nessasary figures. That makes it fast in data changing.

But to be careful, I suggest you to make some performace tests. 1000 points is not a problem at all, but 30ms is a rare requirement that I havent tried.

[entronad]

I hope you could please feedback your result in this issue, whether this lib satisfy your demand at last.

[smofe]

Thanks for the quick response!
I tried to get it to work, but I am unable to update the chart. I feel like I am missing something obvious here. Do you see the mistake?

My code looks like this:

// timer that is started in initState and adds new data points to the data list
timer = Timer.periodic(const Duration(milliseconds: 30), (_) {
      if (data.length >= 1000) {
        data.removeAt(0);
      }
      setState(() {
        data.add(ChartData(counter, r.nextInt(1000)));
      });
      print(data[0]);
      counter++;
    });

Chart(
  rebuild: false,
  changeData: true,
  data: data,
  variables: {
    'index':
        Variable(accessor: (ChartData data) => data.index),
    'value':
        Variable(accessor: (ChartData data) => data.value)
  },
  elements: [
    LineElement(
        shape: ShapeAttr(value: BasicLineShape(smooth: true)))
  ],
  axes: [
    Defaults.horizontalAxis,
    Defaults.verticalAxis,
  ],
)

[entronad]

The problem is caused by a bug, when you didn't create new instance of the data list but modified it, the changeData: true will not work.

It has been fixed in 0.8.0, please upgrade and try.

But I have to say usually we consider widget property as immutable and create new instance when setState in Flutter. That's why this bug is hardly to expose. I suggest you to do so.

[smofe]

Thank you! I got it working now.

First impressions are that performance is adequat, although it is pushing it to the limit. Pretty much comparable to Syncfusion Charts, which I used before. I've got some issues with stuttering where I don't know yet what causes the problem, but so far I think it's not related to this library, as similar issues occured with the Syncfusion one.

I will do further testing and report back when I know more.

[jiangweihu]

Thank you! I got it working now.

First impressions are that performance is adequat, although it is pushing it to the limit. Pretty much comparable to Syncfusion Charts, which I used before. I've got some issues with stuttering where I don't know yet what causes the problem, but so far I think it's not related to this library, as similar issues occured with the Syncfusion one.

I will do further testing and report back when I know more.

Hello, I'm working on something similar, updating the data every second and then plotting a line graph of the data in real time, can you share your code with me?