javascript - d3 中的分组和汇总

Question

我的代码有问题。这是示例数据看起来像

var data = [
{
"office": "George Town Office",
"city_name": "George Town",
"total_employee": 2100,
},
{
"office": "George Town Working Space",
"city_name": "George Town",
"total_employee": 100,
},
{
"office": "Renasti KL Office",
"city_name": "Kuala Lumpur",
"total_employee": 1900,
}
]

我用键 (city_name) 将它分组，如果我需要计算 total_employee，我会遇到汇总问题。这是代码

var nested_data =  d3.nest()
    .key(function(d) {  return d.city_name; })
    //error undefined .rollup(function(v, i) { return v.total_employee; })
    .entries(da);

控制台结果示例如下

0:
key: "George Town"
values: Array(8)
0: {city_name: "George Town", office: "George Town Office", total_employee: 2100, …}
1: {city_name: "George Town", office: "George Town Office Working Space", total_employee: 100, …}

我的问题是如何计算同一个键中的 total_employee？预期结果

key: "George Town"
values: total_employee: 2200

Answer 1

在您的rollup 方法中...

.rollup(function(v, i) { return v.total_employee; })

... v 是一个对象数组，而不是单个对象。因此，您应该将其作为数组进行威胁，例如使用 d3.sum:

.rollup(function(v) {
    return d3.sum(v, function(e) {
        return e.total_employee;
    })
})

这是演示:

var data = [{
    "office": "George Town Office",
    "city_name": "George Town",
    "total_employee": 2100,
  },
  {
    "office": "George Town Working Space",
    "city_name": "George Town",
    "total_employee": 100,
  },
  {
    "office": "Renasti KL Office",
    "city_name": "Kuala Lumpur",
    "total_employee": 1900,
  }
]

var nested_data = d3.nest()
  .key(function(d) {
    return d.city_name;
  })
  .rollup(function(v) {
    return d3.sum(v, function(e) {
      return e.total_employee;
    })
  })
  .entries(data);

console.log(nested_data)

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