获取数组 JavaScript 中的平均值

Question

您好，我有一个如下所示的数组：

[
  {
    group: "23",
    delays: [
      { Station: "a", Arrival: "3", Departure: 0 },
      { Station: "b", Arrival: -179, Departure: 0 },
      { Station: "c", Arrival: -156, Departure: 0 },
    ],
  },
  {
    group: "23",
    delays: [
      { Station: "a", Arrival: "5", Departure: 79 },
      { Station: "b", Arrival: 0, Departure: 0 },
      { Station: "c", Arrival: 68, Departure: 68 },
    ],
  },
];

到目前为止，我已经能够消除重复项并将变量相加......但是我希望获得这些值的平均值而不是求和它们。 这是总结它们的代码，合并“计算平均值”功能的最佳方法是什么？假设 Station b 出现两次，那么我会将 Station b 的总和除以 2。

var dataPoints = [];
var xs = [];
var n = [];

function addData(data) {
    for (var i = 0; i < data.length; i++) {
        for (var j = 0; j < data[i].delays.length; j++) {
            dataPoints.push({
                x: data[i].delays[j].Station,
                y: data[i].delays[j].Arrival
            });
        }
    }
    
    values = ["no information"]
    dataPoints = dataPoints.filter(item => !values.includes(item.y));
    
    dataPoints.forEach((e) => {
        if (!xs.includes(e.x)) { n.push(e); xs.push(e.x) }
        else { n.forEach(f => f.y += f.x == e.x ? e.y : 0) }
        // make a change here to get average of duplicate stations  
        // Say Station b appears twice, then I would divide sum of 
        // Station b by two.
    })

    console.log(n)

Answer 1

得到dataPoints后的代码

const map = new Map();
  dataPoints.forEach(({ x, y }) => {
    const [total, count] = map.get(x) ?? [null, 0];
    map.set(x, [(total ?? 0) + parseInt(y), count + 1]);
  });

  n = [...map].map(([k, v]) => ({ x: k, y: v[0] / v[1] }));

我在第一个对象中复制了电台 c。

我在这里使用map 将total 和count 存储在一个数组中。

const data = [
  {
    group: "23",
    delays: [
      { Station: "a", Arrival: "3", Departure: 0 },
      { Station: "b", Arrival: -179, Departure: 0 },
      { Station: "c", Arrival: -156, Departure: 0 },
      { Station: "c", Arrival: 157, Departure: 0 },
    ],
  },
  {
    group: "23",
    delays: [
      { Station: "d", Arrival: "5", Departure: 79 },
      { Station: "f", Arrival: 0, Departure: 0 },
      { Station: "g", Arrival: 68, Departure: 68 },
    ],
  },
];

var dataPoints = [];
var xs = [];
var n = [];

function addData(data) {
  for (var i = 0; i < data.length; i++) {
    for (var j = 0; j < data[i].delays.length; j++) {
      dataPoints.push({
        x: data[i].delays[j].Station,
        y: data[i].delays[j].Arrival,
      });
    }
  }

  values = ["no information"];
  dataPoints = dataPoints.filter((item) => !values.includes(item.y));

  const map = new Map();
  dataPoints.forEach(({ x, y }) => {
    const [total, count] = map.get(x) ?? [null, 0];
    map.set(x, [(total ?? 0) + parseInt(y), count + 1]);
  });

  n = [...map].map(([k, v]) => ({ x: k, y: v[0] / v[1] }));
  console.log(n);
}

addData(data);

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