mathtool2/lib/tools/chi_square.dart

// tools/chi_square.dart
import 'package:fl_chart/fl_chart.dart';
import 'package:flutter/material.dart';

import 'tool_kit.dart';

/// 卡方检验（2×2 列联表）。
///
///     K² = n(ad − bc)² / ((a+b)(c+d)(a+c)(b+d))，n = a+b+c+d
///
/// 精确值给分数、近似值给小数，都从 Symja 拿。图表里的比例数据同样走 Symja
/// （`N[...]`），Dart 只负责把数字喂给 fl_chart —— 图表不参与复制。
class ChiSquarePage extends StatefulWidget {
  const ChiSquarePage({super.key});

  @override
  State<ChiSquarePage> createState() => _ChiSquarePageState();
}

class _ChiSquarePageState extends State<ChiSquarePage> {
  final _a = ToolField('a', hint: '第一行左');
  final _b = ToolField('b', hint: '第一行右');
  final _c = ToolField('c', hint: '第二行左');
  final _d = ToolField('d', hint: '第二行右');

  @override
  Widget build(BuildContext context) => ToolScaffold(
        title: '卡方检验',
        fields: [_a, _b, _c, _d],
        intro: const Text('请输入 2×2 列联表数据:'),
        compute: (session) async {
          final a = _need(_a);
          final b = _need(_b);
          final c = _need(_c);
          final d = _need(_d);
          final bind = 'a=$a,b=$b,c=$c,d=$d';

          final k2 = 'With[{$bind}, Module[{nn=a+b+c+d}, '
              'nn*(a*d-b*c)^2/((a+b)*(c+d)*(a+c)*(b+d))]]';

          // 各组比例（给图表，不复制）：组1 = a/(a+b)、b/(a+b)，组2 = c/(c+d)、d/(c+d)
          final prop =
              'With[{$bind}, N[{a/(a+b), b/(a+b), c/(c+d), d/(c+d)}]]';
          final p = parseSymjaList((await session.compute(prop)).text);
          final n0 = p.isNotEmpty ? asNumber(p[0]) ?? 0.0 : 0.0;
          final n1 = p.length > 1 ? asNumber(p[1]) ?? 0.0 : 0.0;
          final n2 = p.length > 2 ? asNumber(p[2]) ?? 0.0 : 0.0;
          final n3 = p.length > 3 ? asNumber(p[3]) ?? 0.0 : 0.0;

          return [
            ...await exactAndApprox(session, 'K²', k2),
            ToolChart('各组比例', _barChart(n0, n1, n2, n3)),
          ];
        },
      );

  /// 等高堆积条形图：两组各按 类别A / 类别B 的比例堆积，纵轴百分比。
  Widget _barChart(double a1, double b1, double a2, double b2) => Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          SizedBox(
            height: 220,
            child: BarChart(
              BarChartData(
                alignment: BarChartAlignment.spaceAround,
                maxY: 1.0,
                barTouchData: BarTouchData(enabled: false),
                titlesData: FlTitlesData(
                  show: true,
                  bottomTitles: AxisTitles(
                    sideTitles: SideTitles(
                      showTitles: true,
                      getTitlesWidget: (value, meta) =>
                          Text(value.toInt() == 0 ? '组1' : '组2'),
                    ),
                  ),
                  leftTitles: AxisTitles(
                    sideTitles: SideTitles(
                      showTitles: true,
                      reservedSize: 40,
                      getTitlesWidget: (value, meta) =>
                          Text('${(value * 100).toInt()}%'),
                    ),
                  ),
                  topTitles: AxisTitles(
                    sideTitles: SideTitles(showTitles: false),
                  ),
                  rightTitles: AxisTitles(
                    sideTitles: SideTitles(showTitles: false),
                  ),
                ),
                gridData: FlGridData(
                  show: true,
                  drawVerticalLine: false,
                  getDrawingHorizontalLine: (value) => FlLine(
                    color: Colors.grey.withValues(alpha: 0.3),
                    strokeWidth: 1,
                  ),
                ),
                borderData: FlBorderData(show: false),
                barGroups: [
                  BarChartGroupData(
                    x: 0,
                    groupVertically: true,
                    barsSpace: 4,
                    barRods: [
                      BarChartRodData(
                        fromY: 0,
                        toY: a1,
                        color: Colors.blue,
                        width: 30,
                      ),
                      BarChartRodData(
                        fromY: a1,
                        toY: a1 + b1,
                        color: Colors.red,
                        width: 30,
                      ),
                    ],
                  ),
                  BarChartGroupData(
                    x: 1,
                    groupVertically: true,
                    barsSpace: 4,
                    barRods: [
                      BarChartRodData(
                        fromY: 0,
                        toY: a2,
                        color: Colors.blue,
                        width: 30,
                      ),
                      BarChartRodData(
                        fromY: a2,
                        toY: a2 + b2,
                        color: Colors.red,
                        width: 30,
                      ),
                    ],
                  ),
                ],
              ),
            ),
          ),
          const SizedBox(height: 10),
          Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              _legend(Colors.blue, '类别A'),
              const SizedBox(width: 20),
              _legend(Colors.red, '类别B'),
            ],
          ),
        ],
      );

  Widget _legend(Color color, String text) => Row(
        mainAxisSize: MainAxisSize.min,
        children: [
          Container(width: 16, height: 16, color: color),
          const SizedBox(width: 8),
          Text(text),
        ],
      );

  /// 取一个标量输入框：空着或填了多个值都直接报中文错。
  String _need(ToolField f) {
    if (f.count == 0) throw Exception('请填写「${f.label}」');
    if (f.count > 1) throw Exception('「${f.label}」只能填一个数');
    return f.text;
  }
}