javascript - 如何过滤 json 并获取在 js 中创建线图的平均值？

Question

我有 json 格式的数据，所以我想用 plotly js 绘图，我需要按学期创建不同州的图，所以我需要过滤每个州(例如加利福尼亚州)，然后我需要得到每个学期的平均值，最后绘制它。

到目前为止我有这段代码，但我不知道如何在 js 中过滤 im new

// Trace1 
var trace1 = {
  x: data.map(row => row.date),
  y: data.map(row => row.snap_biannual_chan),
  text: data.map(row => row.state_name),
  name: "snap_biannual_chan",
  type: "line"
};

// Combining both traces
var data = [trace1];

// Apply the group barmode to the layout
var layout = {
  title: "Practice",
  xaxis: {
    categoryorder: "array",
  }
};

// Render the plot to the div tag with id "plot"
Plotly.newPlot("plot", data, layout)

这是 json 示例:

“county_state_id”:“06001”， "pop_hispan_prop": ".1176472187212034", “pop_un_st”:3059000， "state_name": "加州", "county_name": "阿拉米达县", “pop_un_co”:109000， "state_id": "06", "county_id": "001", “pop_co”:1605217， “pop_st”:38654206， "state_abbrev": "CA", “学期”:“0118”， “快照受益人”:102034， “snap_biannual_chan”:-2.02980374083036， "sem": "18 月 18 日", “pop_un_co_per”:6.790359185082141， “pop_un_st_per”:7.913757173022776， “年”:2018年， “月”:1， "日期": "2018年1月"

Answer 1

您可以使用数组 filter() 和 reduce() 方法来计算均值，而无需对一堆循环和变量进行微观管理。这是一个例子:

const data = [
  { state_id: "01", snap_biannual_chan: 5.5 },
  { state_id: "01", snap_biannual_chan: 3 },
  { state_id: "02", snap_biannual_chan: 5 }
];

const state01 = data.filter(x => x.state_id === "01");
const meanState01 = state01.reduce((acc, item) => {
  acc.sum += item.snap_biannual_chan;
  acc.mean = acc.sum / state01.length 
  return acc;
}, { sum: 0, mean: 0 });

console.log(meanState01);
console.log("the mean: ", meanState01.mean);