szjs/pages/heightSdsCalculator/heightSdsCalculator.js

const app = getApp();

// 添加正态分布相关的数学函数
const normalDistribution = {
  // 误差函数的近似计算
  erf(x) {
    // 误差函数的系数
    const a1 = 0.254829592;
    const a2 = -0.284496736;
    const a3 = 1.421413741;
    const a4 = -1.453152027;
    const a5 = 1.061405429;
    const p = 0.3275911;

    // 取绝对值
    const sign = (x >= 0) ? 1 : -1;
    x = Math.abs(x);

    // 误差函数近似公式的计算
    const t = 1.0 / (1.0 + p * x);
    const y = 1.0 - (((((a5 * t + a4) * t) + a3) * t + a2) * t + a1) * t * Math.exp(-x * x);

    return sign * y;
  },

  // 计算百分位数
  calculatePercentile(sds) {
    return (1 + this.erf(sds / Math.sqrt(2))) / 2 * 100;
  }
};

Page({
  data: {
    // 基础数据
    age: '',
    height: '',
    gender: 'male',
    // 计算结果
    showResult: false,
    sdsValue: null,
    calculationDetails: null,
    growthEvaluation: '',
    // 参考数据
    standardData: {
      male: [
        { age: 1, mean: 76.5, sd: 3.0 },
        { age: 2, mean: 88.5, sd: 3.5 },
        { age: 3, mean: 96.8, sd: 3.8 },
        { age: 4, mean: 103.5, sd: 4.2 },
        { age: 5, mean: 110.0, sd: 4.5 },
        { age: 6, mean: 116.5, sd: 4.8 },
        { age: 7, mean: 124.0, sd: 5.0 },
        { age: 8, mean: 129.5, sd: 5.2 },
        { age: 9, mean: 134.5, sd: 5.5 },
        { age: 10, mean: 138.5, sd: 5.8 },
        { age: 11, mean: 143.0, sd: 6.0 },
        { age: 12, mean: 150.0, sd: 6.5 },
        { age: 13, mean: 156.5, sd: 7.0 },
        { age: 14, mean: 163.0, sd: 7.2 },
        { age: 15, mean: 168.0, sd: 6.2 },
        { age: 16, mean: 171.5, sd: 5.8 },
        { age: 17, mean: 173.5, sd: 5.5 },
        { age: 18, mean: 174.5, sd: 5.2 }
      ],
      female: [
        { age: 1, mean: 75.0, sd: 2.9 },
        { age: 2, mean: 87.2, sd: 3.4 },
        { age: 3, mean: 95.6, sd: 3.7 },
        { age: 4, mean: 102.5, sd: 4.0 },
        { age: 5, mean: 108.5, sd: 4.3 },
        { age: 6, mean: 115.0, sd: 4.6 },
        { age: 7, mean: 122.5, sd: 4.8 },
        { age: 8, mean: 127.5, sd: 5.0 },
        { age: 9, mean: 132.5, sd: 5.2 },
        { age: 10, mean: 137.0, sd: 5.5 },
        { age: 11, mean: 142.0, sd: 5.8 },
        { age: 12, mean: 148.0, sd: 6.0 },
        { age: 13, mean: 154.0, sd: 6.2 },
        { age: 14, mean: 158.5, sd: 5.8 },
        { age: 15, mean: 160.5, sd: 5.5 },
        { age: 16, mean: 161.5, sd: 5.2 },
        { age: 17, mean: 162.0, sd: 5.0 },
        { age: 18, mean: 162.5, sd: 4.8 }
      ]
    }
  },

  // 输入处理
  inputAge(e) {
    this.setData({
      age: Number(e.detail.value)
    });
  },

  inputHeight(e) {
    this.setData({
      height: Number(e.detail.value)
    });
  },

  selectGender(e) {
    this.setData({
      gender: e.currentTarget.dataset.gender
    });
  },

  // 计算SDS
  calculate() {
    const { age, height, gender } = this.data;
    
    // 输入验证
    if (!this.validateInput(age, height)) return;

    try {
      // 获取标准数据
      const standardData = this.getStandardData(age, gender);
      if (!standardData) {
        throw new Error('未找到对应年龄的标准数据');
      }

      // 计算SDS
      const sds = this.calculateSDS(
        Number(height), 
        Number(standardData.mean), 
        Number(standardData.sd)
      );
      
      // 计算中间值，用于显示
      const difference = Number(height) - Number(standardData.mean);
      
      // 获取评价
      const evaluation = this.getGrowthEvaluation(sds);

      // 显示结果
      this.setData({
        showResult: true,
        sdsValue: Number(sds.toFixed(2)),
        calculationDetails: {
          height: Number(height).toFixed(1),
          mean: Number(standardData.mean).toFixed(1),
          sd: Number(standardData.sd).toFixed(1),
          formula: `身高SDS = (${height} - ${standardData.mean}) / ${standardData.sd}`,
          calculation: `         = (${height} - ${standardData.mean}) / ${standardData.sd}`,
          difference: `         = ${difference.toFixed(1)} / ${standardData.sd}`,
          result: `         = ${sds.toFixed(2)}`,
          interpretation: this.getInterpretation(sds)
        },
        growthEvaluation: evaluation
      });

    } catch (error) {
      wx.showToast({
        title: error.message || '计算失败',
        icon: 'none'
      });
    }
  },

  // 输入验证
  validateInput(age, height) {
    if (!age || !height) {
      wx.showToast({
        title: '请填写完整信息',
        icon: 'none'
      });
      return false;
    }

    if (age < 1 || age > 18) {
      wx.showToast({
        title: '年龄必须在1-18岁之间',
        icon: 'none'
      });
      return false;
    }

    if (height <= 0) {
      wx.showToast({
        title: '身高必须大于0',
        icon: 'none'
      });
      return false;
    }

    return true;
  },

  // 获取标准数据
  getStandardData(age, gender) {
    return this.data.standardData[gender].find(item => item.age === age);
  },

  // 计算SDS值
  calculateSDS(height, mean, sd) {
    // 输入验证
    if (typeof height !== 'number' || typeof mean !== 'number' || typeof sd !== 'number') {
      throw new Error('输入参数必须为数字');
    }

    // SDS = (个体身高 - 平均身高) / 标准差
    const sds = (height - mean) / sd;
    
    // 验证计算结果
    if (isNaN(sds) || !isFinite(sds)) {
      throw new Error('计算结果无效');
    }

    // 计算过程已隐藏

    return sds;
  },

  // 获取生长评价
  getGrowthEvaluation(sds) {
    // 根据标准更新评价标准
    if (sds < -2) {
      return '可能存在生长迟缓';
    } else if (sds > 2) {
      return '可能存在生长过快';
    } else {
      return '正常范围';
    }
  },

  // 重置表单
  reset() {
    this.setData({
      age: '',
      height: '',
      gender: 'male',
      showResult: false,
      sdsValue: null,
      calculationDetails: null,
      growthEvaluation: ''
    });
  },

  // 返回上一页
  onClickLeft() {
    wx.navigateBack();
  },

  // 修改计算百分位数的方法
  calculatePercentile(sds) {
    const percentile = normalDistribution.calculatePercentile(sds);
    return percentile.toFixed(1);
  },

  // 获取解释文本
  getInterpretation(sds) {
    const percentile = this.calculatePercentile(sds);
    let interpretation = `身高SDS值：${sds.toFixed(2)}\n`;
    interpretation += `该儿童身高位于同年龄同性别儿童的第${percentile}百分位\n`;
    
    // 根据SDS值添加解释
    if (sds === 0) {
      interpretation += '身高等于平均值';
    } else if (sds > 0) {
      interpretation += `高于平均值${(Math.abs(sds) * 100).toFixed(1)}%`;
    } else {
      interpretation += `低于平均值${(Math.abs(sds) * 100).toFixed(1)}%`;
    }
    
    return interpretation;
  }
});