mathtool/lib/tools/regression.dart

// tools/regression.dart
import 'package:flutter/material.dart';
import 'package:rational/rational.dart';
import '../utils/math_utils.dart';
import 'dart:math';
import 'package:fl_chart/fl_chart.dart';

class RegressionPage extends StatefulWidget {
  @override
  _RegressionPageState createState() => _RegressionPageState();
}

class _RegressionPageState extends State<RegressionPage> {
  final TextEditingController xController = TextEditingController();
  final TextEditingController yController = TextEditingController();

  String result = '';
  List<FlSpot> scatterSpots = [];
  List<FlSpot> regressionLineSpots = [];
  bool showRegressionLine = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('线性回归')),
      body: SingleChildScrollView( // 添加可滚动容器
        padding: EdgeInsets.all(16), // 将padding移到这里
        child: Column(
          children: [
            _buildInputField('x值（用空格分隔）', xController),
            _buildInputField('y值（用空格分隔）', yController),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: _calculate,
              child: Text('计算'),
            ),
            SizedBox(height: 20),
            // 回归直线显示选项
            Row(
              children: [
                Checkbox(
                  value: showRegressionLine,
                  onChanged: (value) {
                    setState(() {
                      showRegressionLine = value!;
                    });
                  },
                ),
                Text('显示回归直线'),
              ],
            ),
            SizedBox(height: 20),
            if (result.isNotEmpty)
              Card(
                child: Padding(
                  padding: EdgeInsets.all(16),
                  child: Text(
                    result,
                    style: TextStyle(fontSize: 14, fontFamily: 'Monospace'),
                  ),
                ),
              ),
            SizedBox(height: 20),
            // 散点图
            if (scatterSpots.isNotEmpty) _buildScatterChart(),
          ],
        ),
      ),
    );
  }

  Widget _buildInputField(String label, TextEditingController controller) {
    return Padding(
      padding: EdgeInsets.symmetric(vertical: 8),
      child: TextField(
        controller: controller,
        keyboardType: TextInputType.numberWithOptions(signed: true, decimal: true),
        decoration: InputDecoration(
          labelText: label,
          border: OutlineInputBorder(),
          hintText: '用空格分隔多个值',
        ),
      ),
    );
  }

  Widget _buildScatterChart() {
    return Container(
      height: 300,
      padding: EdgeInsets.all(16),
      child: Card(
        elevation: 4,
        child: Padding(
          padding: EdgeInsets.all(16),
          child: LineChart(
            LineChartData(
              gridData: FlGridData(show: true),
              titlesData: FlTitlesData(
                bottomTitles: AxisTitles(
                  sideTitles: SideTitles(showTitles: true),
                ),
                leftTitles: AxisTitles(
                  sideTitles: SideTitles(showTitles: true),
                ),
                topTitles: AxisTitles(sideTitles: SideTitles(showTitles: false)),
                rightTitles: AxisTitles(sideTitles: SideTitles(showTitles: false)),
              ),
              borderData: FlBorderData(show: true),
              minX: scatterSpots.map((spot) => spot.x).reduce(min) - 1,
              maxX: scatterSpots.map((spot) => spot.x).reduce(max) + 1,
              minY: scatterSpots.map((spot) => spot.y).reduce(min) - 1,
              maxY: scatterSpots.map((spot) => spot.y).reduce(max) + 1,
              lineBarsData: [
                // 散点图
                LineChartBarData(
                  spots: scatterSpots,
                  isCurved: false,
                  dotData: FlDotData(
                    show: true,
                    getDotPainter: (spot, percent, barData, index) {
                      return FlDotCirclePainter(
                        radius: 4,
                        color: Colors.blue,
                        strokeWidth: 2,
                        strokeColor: Colors.blue,
                      );
                    },
                  ),
                  color: Colors.transparent, // 隐藏连接线
                  belowBarData: BarAreaData(show: false),
                ),
                // 回归直线（可选）
                if (showRegressionLine && regressionLineSpots.isNotEmpty)
                  LineChartBarData(
                    spots: regressionLineSpots,
                    isCurved: false,
                    dotData: FlDotData(show: false),
                    color: Colors.red,
                    barWidth: 2,
                    belowBarData: BarAreaData(show: false),
                  ),
              ],
            ),
          ),
        ),
      ),
    );
  }

  void _calculate() {
    try {
      final xList = xController.text.split(' ').where((s) => s.isNotEmpty).map((s) => double.parse(s)).toList();
      final yList = yController.text.split(' ').where((s) => s.isNotEmpty).map((s) => double.parse(s)).toList();

      if (xList.isEmpty || yList.isEmpty) {
        setState(() {
          result = '错误: 请输入数据';
        });
        return;
      }

      if (xList.length != yList.length) {
        setState(() {
          result = '错误: x和y的数据长度不一致';
        });
        return;
      }

      final n = xList.length;
      double sx = 0, sy = 0, sx2 = 0, sy2 = 0, sxy = 0;

      for (int i = 0; i < n; i++) {
        sx += xList[i];
        sy += yList[i];
        sx2 += xList[i] * xList[i];
        sy2 += yList[i] * yList[i];
        sxy += xList[i] * yList[i];
      }

      final xBar = sx / n;
      final yBar = sy / n;
      final sigmaX = sx2 - n * xBar * xBar;
      final sigmaY = sy2 - n * yBar * yBar;
      final sigmaXY = sxy - n * xBar * yBar;

      final r = sigmaXY / sqrt(sigmaX * sigmaY);
      final b = sigmaXY / sigmaX;
      final a = yBar - b * xBar;

      double se2 = 0;
      for (int i = 0; i < n; i++) {
        se2 += pow(yList[i] - b * xList[i] - a, 2);
      }
      final R2 = 1 - se2 / sigmaY;

      // 准备散点数据
      scatterSpots = [];
      for (int i = 0; i < n; i++) {
        scatterSpots.add(FlSpot(xList[i], yList[i]));
      }

      // 准备回归直线数据（两个端点）
      regressionLineSpots = [];
      if (xList.isNotEmpty) {
        double minX = xList.reduce(min);
        double maxX = xList.reduce(max);
        regressionLineSpots.add(FlSpot(minX, a + b * minX));
        regressionLineSpots.add(FlSpot(maxX, a + b * maxX));
      }

      setState(() {
        result = '''
      x_bar = ${xBar.toStringAsFixed(4)}
      y_bar = ${yBar.toStringAsFixed(4)}
      Σ(x-x̄)² = ${sigmaX.toStringAsFixed(4)}
      Σ(y-ȳ)² = ${sigmaY.toStringAsFixed(4)}
      Σ(x-x̄)(y-ȳ) = ${sigmaXY.toStringAsFixed(4)}
      相关系数 r = ${r.toStringAsFixed(4)}
      斜率 b = ${b.toStringAsFixed(4)}
      截距 a = ${a.toStringAsFixed(4)}
      残差平方和 = ${se2.toStringAsFixed(4)}
      决定系数 R² = ${R2.toStringAsFixed(4)}
      ''';
      });
    } catch (e) {
      setState(() {
        result = '错误: $e';
        scatterSpots = [];
        regressionLineSpots = [];
      });
    }
  }

  @override
  void dispose() {
    xController.dispose();
    yController.dispose();
    super.dispose();
  }
}