mathtool/lib/tools/histogram.dart

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

class HistogramPage extends StatefulWidget {
  @override
  _HistogramPageState createState() => _HistogramPageState();
}

class _HistogramPageState extends State<HistogramPage> {
  final TextEditingController leftEndpointController = TextEditingController();
  final TextEditingController groupDistanceController = TextEditingController();
  final TextEditingController frequenciesController = TextEditingController();
  final TextEditingController percentileController = TextEditingController();

  String result = '';
  List<BarChartGroupData>? barGroups;
  List<String>? groupLabels;
  double? maxFrequencyDensity;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('直方图统计')),
      body: SingleChildScrollView( // 添加滚动视图
        padding: EdgeInsets.all(16),
        child: Column(
          children: [
            _buildInputField('左端点', leftEndpointController),
            _buildInputField('组距', groupDistanceController),
            _buildInputField('各组频率（用空格分隔）', frequenciesController),
            _buildInputField('百分位数（可选）', percentileController),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: _calculate,
              child: Text('计算'),
            ),
            SizedBox(height: 20),
            if (result.isNotEmpty)
              Card(
                child: Padding(
                  padding: EdgeInsets.all(16),
                  child: Text(
                    result,
                    style: TextStyle(fontSize: 14, fontFamily: 'Monospace'),
                  ),
                ),
              ),
            if (barGroups != null && barGroups!.isNotEmpty)
              SizedBox( // 将 Expanded 改为 SizedBox 并指定高度
                height: 400, // 设置固定高度
                child: Card(
                  child: Padding(
                    padding: EdgeInsets.all(16),
                    child: Column(
                      children: [
                        Text(
                          '直方图',
                          style: TextStyle(
                            fontSize: 18,
                            fontWeight: FontWeight.bold,
                          ),
                        ),
                        SizedBox(height: 10),
                        Expanded( // 这个 Expanded 可以保留，因为它是在 Column 内部
                          child: BarChart(
                            BarChartData(
                              barGroups: barGroups,
                              alignment: BarChartAlignment.spaceBetween,
                              groupsSpace: 0,
                              barTouchData: BarTouchData(
                                enabled: false,
                              ),
                              borderData: FlBorderData(show: true),
                              gridData: FlGridData(show: false),
                              titlesData: FlTitlesData(
                                bottomTitles: AxisTitles(
                                  sideTitles: SideTitles(
                                    showTitles: true,
                                    getTitlesWidget: (value, meta) {
                                      final index = value.toInt();
                                      if (index >= 0 && index < (groupLabels?.length ?? 0)) {
                                        return Padding(
                                          padding: const EdgeInsets.only(top: 8.0),
                                          child: Text(
                                            groupLabels![index],
                                            style: TextStyle(
                                              fontSize: 10,
                                              fontWeight: FontWeight.bold,
                                            ),
                                            textAlign: TextAlign.center,
                                          ),
                                        );
                                      }
                                      return Text('');
                                    },
                                    reservedSize: 40,
                                  ),
                                ),
                                leftTitles: AxisTitles(
                                  sideTitles: SideTitles(
                                    showTitles: true,
                                    reservedSize: 40,
                                    getTitlesWidget: (value, meta) {
                                      return Text(value.toStringAsFixed(2));
                                    },
                                  ),
                                ),
                                rightTitles: AxisTitles(
                                  sideTitles: SideTitles(showTitles: false),
                                ),
                                topTitles: AxisTitles(
                                  sideTitles: SideTitles(showTitles: false),
                                ),
                              ),
                              maxY: maxFrequencyDensity != null 
                                  ? (maxFrequencyDensity! * 1.1)
                                  : 1.0,
                            ),
                          ),
                        ),
                      ],
                    ),
                  ),
                ),
              ),
          ],
        ),
      ),
    );
  }

  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: label.contains('频率') ? '用空格分隔多个值' : '输入分数如: 1/2 或小数',
        ),
      ),
    );
  }

  void _calculate() {
    try {
      final a = MathUtils.parseRational(leftEndpointController.text);
      final d = MathUtils.parseRational(groupDistanceController.text);
      final frequencies = frequenciesController.text.split(' ').map((s) => MathUtils.parseRational(s)).toList();

      Rational sumFreq = MathUtils.zero;
      for (final f in frequencies) {
        sumFreq += f;
      }

      if (sumFreq != MathUtils.one) {
        setState(() {
          result = '错误: 频率之和必须为1，当前为 ${MathUtils.rationalToString(sumFreq)}';
          barGroups = null;
          groupLabels = null;
        });
        return;
      }

      // 计算均值
      Rational mean = MathUtils.zero;
      for (int i = 0; i < frequencies.length; i++) {
        mean += (a + MathUtils.fromInt(i) * d + d / MathUtils.two) * frequencies[i];
      }

      // 计算方差
      Rational variance = MathUtils.zero;
      for (int i = 0; i < frequencies.length; i++) {
        final midPoint = a + MathUtils.fromInt(i) * d + d / MathUtils.two;
        variance += (midPoint - mean).pow(2) * frequencies[i];
      }

      String output = '均值: ${MathUtils.rationalToString(mean)} (近似值: ${mean.toDouble()})\n'
      '方差: ${MathUtils.rationalToString(variance)} (近似值: ${variance.toDouble()})\n';

      // 计算中位数
      Rational cumulative = MathUtils.zero;
      for (int i = 0; i < frequencies.length; i++) {
        if (cumulative + frequencies[i] > MathUtils.half) {
          final median = a + MathUtils.fromInt(i) * d - (cumulative - MathUtils.half) / frequencies[i] * d;
          output += '中位数: ${MathUtils.rationalToString(median)} (近似值: ${median.toDouble()})\n';
          break;
        }
        cumulative += frequencies[i];
      }

      // 计算百分位数
      if (percentileController.text.isNotEmpty) {
        final p = MathUtils.parseRational(percentileController.text);
        cumulative = MathUtils.zero;
        for (int i = 0; i < frequencies.length; i++) {
          if (cumulative + frequencies[i] > p) {
            final percentile = a + MathUtils.fromInt(i) * d - (cumulative - p) / frequencies[i] * d;
            output += '${MathUtils.rationalToString(p)} 百分位数: ${MathUtils.rationalToString(percentile)} (近似值: ${percentile.toDouble()})';
            break;
          }
          cumulative += frequencies[i];
        }
      }

      // 生成直方图数据
      _generateHistogramData(a, d, frequencies);

      setState(() {
        result = output;
      });
    } catch (e) {
      setState(() {
        result = '错误: $e';
        barGroups = null;
        groupLabels = null;
      });
    }
  }

  void _generateHistogramData(Rational a, Rational d, List<Rational> frequencies) {
    barGroups = [];
    groupLabels = [];
    maxFrequencyDensity = 0.0;

    for (int i = 0; i < frequencies.length; i++) {
      final left = a + MathUtils.fromInt(i) * d;
      final right = left + d;
      
      // 计算频率/组距作为纵坐标
      final frequencyDensity = (frequencies[i] / d).toDouble();
      
      // 更新最大频率密度
      if (frequencyDensity > maxFrequencyDensity!) {
        maxFrequencyDensity = frequencyDensity;
      }

      barGroups!.add(
        BarChartGroupData(
          x: i,
          barRods: [
            BarChartRodData(
              toY: frequencyDensity,
              width: 16,
              color: Colors.blue,
              borderRadius: BorderRadius.zero,
            ),
          ],
        ),
      );

      groupLabels!.add(
        '[${MathUtils.rationalToString(left)}, ${MathUtils.rationalToString(right)})',
      );
    }

    // 确保maxFrequencyDensity不为0
    if (maxFrequencyDensity == 0.0) {
      maxFrequencyDensity = 1.0;
    }
  }

  @override
  void dispose() {
    leftEndpointController.dispose();
    groupDistanceController.dispose();
    frequenciesController.dispose();
    percentileController.dispose();
    super.dispose();
  }
}