angular - 如何在Angular 10中获取表中多列的平均值

Question

我有计算表上所有列中 json 数据总和的函数。我想获得每列的平均值，但最终得到 NaN 或无穷大，我做错了什么？
这是我获取总和的实现

getSum(columnNumber) {
    let sum = 0;
    const columnNumberToPropertyMap = [
      "id",
      "teamNumber",
      "rural",
      "completed",
      "entirehouseholdabsent",
      "postponed",
      "refused",
      "vacant",
      "dwelling"     
    ];
    const property = columnNumberToPropertyMap[columnNumber];
    return this.rural.reduce((acc, curr) => {
      //const adder = Number(curr[property]) || 0;
      const adder = isNaN(Number(curr[property])) ? 0 : Number(curr[property]);
      sum = acc + adder
      return sum;
    }, 0).toFixed(2);
  }

这给了我列中所有行的总和。
我如何尝试获得每列的平均值

 getSum(columnNumber) {
        let sum = 0;
        let average = 0;

        const columnNumberToPropertyMap = [
          "id",
          "teamNumber",
          "rural",
          "completed",
          "entirehouseholdabsent",
          "postponed",
          "refused",
          "vacant",
          "dwelling"     
        ];
        const property = columnNumberToPropertyMap[columnNumber];
        return this.rural.reduce((acc, curr) => {
          //const adder = Number(curr[property]) || 0;
          const adder = isNaN(Number(curr[property])) ? 0 : Number(curr[property]);
          sum = acc + adder
          average = (sum)/adder;
          return average ;
        }, 0).toFixed(2);
      }

我最终在每列的下方得到 NaN 或无穷大，我假设

average = total of each column / no of items on each column

Answer 1

要查找平均值，您只需调用 getSum然后除以行数。因此，实现将是这样的:

getAverage(columnNumber) {
    let sum = getSum(columnNumber);
    let count = this.rural.length;
    return sum / count;
}

或者，在一行中， return getSum(columnNumber)/this.rural.length;