Line chart representation of List containing double values-CodePudding

I have Lists of values containing double type numbers and each of this lists contains about 5000 values. Each of this lists has been collected from a microcontroller within 60 seconds.
I want to create a line chart to show the variance of this values. I tried to use the Spline Chart in Flutter but I cannot manage to make it read values from a list as its throwing this error:

The return type 'List?' isn't a 'num?', as required by the closure's context.

and here is the code:



 Widget build(BuildContext context) {
    final List<ChartData> chartData = [
      ChartData(10, [5.5,0.6]),
      ChartData(20, [2.5,0.6]),
      ChartData(30, [1.5,0.6]),
      ChartData(40, [0.5,0.6]),
      ChartData(50, [0.5,3.6]),
      ChartData(60, [0.5,2.6]),
      ChartData(70, [0.5,1.6]),
      ChartData(80, [0.5,0.63]),
      ChartData(90, [0.5,0.126]),
    ];
    return Scaffold(
        body: Center(
            child: Container(
                child: SfCartesianChart(
                    series: <ChartSeries>[
                      // Renders spline chart
                      SplineSeries<ChartData, int>(
                          dataSource: chartData,
                          xValueMapper: (ChartData data, _) => data.x,
                          yValueMapper: (ChartData data, _) => data.y
                      )
                    ]
                )
            )
        )
    );
  }
}
class ChartData {
  ChartData(this.x, this.y);
  final int x;
  final List? y;
}

I tried to create a list that has few values and called some elements from each list to the chart. It looked like this:

List x =[1.0,1.2,1.3,1.5,1.9,1.8,1.9,2.9,3.9,1.9,1.8,1.4];

  @override
  Widget build(BuildContext context) {
    final List<ChartData> chartData = [
      ChartData(10, x[1]),
      ChartData(20, x[2]),
      ChartData(30, x[0]),
      ChartData(40, x[4]),
      ChartData(50, x[5]),
      ChartData(60, x[6]),
      ChartData(70, x[7]),
      ChartData(80, x[8]),
      ChartData(90, x[9]),
    ];

And this worked for me but Can I make it so I can call all the elemnts from the list to the chart. Do you have any suggestion on how to make this thing happens. thank you in advance

CodePudding user response：

Your y in ChartData is List. And you try to assign it to num?

yValueMapper: (ChartData data, _) => data.y

If the length of y is not fixed, you can use this function to generate SplineSeries

 List<SplineSeries> generateSplineSeries(List<ChartData> chartData){
    List<SplineSeries> splines = [];
    for(int i=0; i<chartData.first.y!.length; i  ){
      splines.add( SplineSeries<ChartData, int>(
        dataSource: chartData,
        xValueMapper: (ChartData data, _) => data.x,
        yValueMapper: (ChartData data, _) => data.y![i],
      ));
    }
    return splines;
  }

Widget build(BuildContext context) {
    final List<ChartData> chartData = [
      ChartData(10, [5.5,0.6]),
      ChartData(20, [2.5,0.6]),
      ChartData(30, [1.5,0.6]),
      ChartData(40, [0.5,0.6]),
      ChartData(50, [0.5,3.6]),
      ChartData(60, [0.5,2.6]),
      ChartData(70, [0.5,1.6]),
      ChartData(80, [0.5,0.63]),
      ChartData(90, [0.5,0.126]),
    ];
    return Scaffold(
        body: Center(
            child: Container(
                child: SfCartesianChart(
                    series: generateSplineSeries(chartData),
                )
            )
        )
    );
  }

CodePudding user response：


@override
  Widget build(BuildContext context) {

    List x =[10.0,1.2,1.3,1.5,1.9,1.8,1.9,2.9,3.9,1.9,1.8,1.4];
    final List<ChartData> chartData = [
      ChartData(60,x),

    ];
    List<SplineSeries> generateSplineSeries(List<ChartData> chartData){
      List<SplineSeries> splines = [];
      for(int i=0; i<chartData.first.y!.length; i  ){
        splines.add( SplineSeries<ChartData, int>(
          dataSource: chartData,
          xValueMapper: (ChartData data, _) => data.x,
          yValueMapper: (ChartData data, _) => data.y![i],
        ));
      }
      return splines;
    }
    return Scaffold(
        body: Center(
            child: Container(
                child: SfCartesianChart(
                    series: generateSplineSeries(chartData),
                )
            )
        )
    );
  }
}
class ChartData {
  ChartData(this.x, this.y);
  final int x;
  final List? y;
}