对多维数组进行分组的更好方法 [英] A better way to group a multidimensional array

问题描述

下面的数据代表[行情，数量，单一值]

The data below represents a [ticker, amount, unitary value]

var data = [
  ['A', 140, 82.4],
  ['B', 100, 55.5],
  ['A', 30, 77.2],
  ['B', 200, 60.1]
];

如何对代码进行分组，并使用JavaScript的Map，Reduce和Filter在新的矩阵中(例如[ticker，金额，平均价格，总价值])计算平均价格和总价值:

How to group by ticker codes, and calculate the average price and total value, using JavaScript’s Map, Reduce, and Filter, in a new matrix like [ticker, amount, average price, total value]:

var newData = [
  ['A', 170, 81.482, 13852], 
  ['B', 300, 58.566, 17570]]
];

这是到目前为止我尝试过的.有一种方法可以使这些代码在最短，更优雅的代码方面更有效?

Here is what I have tried so far. There are a way do to this code more efficient in terms of shortest, elegant code?

var newData = data.map(function(item) {
  return data.filter(function(itemFilter) {
    return itemFilter[0] == item[0];
  })
  .reduce(function(array, item) {
    array[0] = item[0];
    array[1] += item[1];
    array[3] += (item[1] * item[2]);
    array[2] = array[3] / array[1];
    return array;
  }, ['', 0, 0, 0]);
})
//Remove duplicate items
.filter(function(item, index, inputArray) {
  return inputArray.map(function(item) {
    return item[0];
  }).indexOf(item[0]) == index;
});

推荐答案

您可以使用临时对象 this 引用结果数组 newData 并添加位置并以第一个项目为键 this [a [0]] 来计算数组的平均值.

You could use a temporary object this for the reference to the result array newData and add the positions and calculate the average at the array with the first item as key this[a[0]].

var data = [['A', 140, 82.4], ['B', 100, 55.5], ['A', 30, 77.2], ['B', 200, 60.1]],
    newData = [];

data.forEach(function (a) {
    var product = a[1] * a[2];
    if (!this[a[0]]) {
        this[a[0]] = [a[0], 0, 0, 0];
        newData.push(this[a[0]]);
    }
    this[a[0]][1] += a[1];
    this[a[0]][3] += product;
    this[a[0]][2] = this[a[0]][3] / this[a[0]][1];
}, {});

document.write('<pre>' + JSON.stringify(newData, 0, 4) + '</pre>');

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