javascript - 分组并计算 Javascript 数组中属性的均值/平均值

Question

我在其他 stackoverflow 帖子中努力寻找我一直在寻找的解决方案，尽管我强烈认为它必须存在。如果是这样，请向正确的方向转发我。

我正在尝试使用运动数据在 javascript 中做一个非常标准的组。我有以下对象数组:

 const myData = [
    {team: "GSW", pts: 120, ast: 18, reb: 11},
    {team: "GSW", pts: 125, ast: 28, reb: 18},
    {team: "GSW", pts: 110, ast: 35, reb: 47},
    {team: "HOU", pts: 100, ast: 17, reb: 43},
    {team: "HOU", pts: 102, ast: 14, reb: 32},
    {team: "SAS", pts: 127, ast: 21, reb: 25},
    {team: "SAS", pts: 135, ast: 25, reb: 37},
    {team: "SAS", pts: 142, ast: 18, reb: 27}
 ]

我的数据中的每一行都对应于一场特定篮球比赛的结果。简而言之，我想按数据分组，并对分组数据应用均值/平均函数。我期望的结果是:

const groupedData = [
    {team: "GSW", pts: 118.3, ast: 27.0, reb: 25.3},
    {team: "HOU", pts: 101, ast: 15.5, reb: 37.5},
    {team: "SAS", pts: 134.7, ast: 21.3, reb: 29.7} 
] 

我更喜欢在这里使用 vanilla javascript 和 reduce()... 鉴于我对 reduce 的了解，这似乎是最好的方法。我目前正在处理这个问题，如果我能在其他人发布答案之前让它工作，我会发布。

编辑:我的实际数据有大约 30 个键。我希望找到一个解决方案，它只要求我 (a) 仅指定要分组的团队列，并假设它对其余列进行分组，或者 (b) 传递一组统计列(pts、asts 等)。 ) 而不是为每个统计数据创建一行。

谢谢!

Answer 1

一种方法是结合使用 reduce 和 map。

const myData = [
    {team: "GSW", pts: 120, ast: 18, reb: 11},
    {team: "GSW", pts: 125, ast: 28, reb: 18},
    {team: "GSW", pts: 110, ast: 35, reb: 47},
    {team: "HOU", pts: 100, ast: 17, reb: 43},
    {team: "HOU", pts: 102, ast: 14, reb: 32},
    {team: "SAS", pts: 127, ast: 21, reb: 25},
    {team: "SAS", pts: 135, ast: 25, reb: 37},
    {team: "SAS", pts: 142, ast: 18, reb: 27}
 ]
 
 // Calculate the sums and group data (while tracking count)
 const reduced = myData.reduce(function(m, d){
    if(!m[d.team]){
      m[d.team] = {...d, count: 1};
      return m;
    }
    m[d.team].pts += d.pts;
    m[d.team].ast += d.ast;
    m[d.team].reb += d.reb;
    m[d.team].count += 1;
    return m;
 },{});
 
 // Create new array from grouped data and compute the average
 const result = Object.keys(reduced).map(function(k){
     const item  = reduced[k];
     return {
         team: item.team,
         ast: item.ast/item.count,
         pts: item.pts/item.count,
         reb: item.reb/item.count
     }
 })
 
 console.log(JSON.stringify(result,null,4));

编辑:刚看到您对问题的更新。如果您可以白名单(提供要计算的键数组)或黑名单(提供要忽略的键数组)键以编程方式执行此操作，则可以取消每个键的每一行。

const myData = [
    {team: "GSW", pts: 120, ast: 18, reb: 11},
    {team: "GSW", pts: 125, ast: 28, reb: 18},
    {team: "GSW", pts: 110, ast: 35, reb: 47},
    {team: "HOU", pts: 100, ast: 17, reb: 43},
    {team: "HOU", pts: 102, ast: 14, reb: 32},
    {team: "SAS", pts: 127, ast: 21, reb: 25},
    {team: "SAS", pts: 135, ast: 25, reb: 37},
    {team: "SAS", pts: 142, ast: 18, reb: 27}
 ]
 
/**
 * Function which accepts a data array and a list of whitelisted
 * keys to find the average of each key after grouping
 */
function getGroupedData(data, whitelist) {
  // Calculate the sums and group data (while tracking count)
  const reduced = data.reduce(function(m, d) {
    if (!m[d.team]) {
      m[d.team] = { ...d,
        count: 1
      };
      return m;
    }
    whitelist.forEach(function(key) {
      m[d.team][key] += d[key];
    });
    m[d.team].count += 1;
    return m;
  }, {});

  // Create new array from grouped data and compute the average
  return Object.keys(reduced).map(function(k) {
    const item = reduced[k];
    const itemAverage = whitelist.reduce(function(m, key) {
      m[key] = item[key] / item.count;
      return m;
    }, {})
    return {
      ...item, // Preserve any non white-listed keys
      ...itemAverage // Add computed averege for whitelisted keys
    }
  })
}


console.log(JSON.stringify(getGroupedData(myData, ['pts', 'ast', 'reb']), null, 4));