array.map（）的二维数组列的平均值 [英] Average of bidimensional array's columns with array.map()

问题描述

我有一个如下所示的数组：

  var array = [[1,3,9]，
 [4,6,8]，
 [3,7,5]，
 [2,8,4]]; 
  

我想得到每列的平均数，但现在我只是想总结它们。这是我的代码：

  var sum = function（arr）{
 return arr.reduce（function（a， b）{return a + b;}，0）; 
}; 
 
 var tests = array.map（function（v，i）{
 return sum（array.map（function（v）{return v [i];}））
}）; 
 
返回测试; 
  

输出正确地转化了总和，但它似乎与行数一样多（ 4行），而不是3对应于列。这是输出：

  tests = [10，24，26，NULL] 
  

任何想法为什么会发生这种情况？

编辑：
我怎样才能执行只有多少列的计算？

我正在使用 Nenad 的答案给出正确的结果。但是我需要在Google Sheets的脚本编辑器中实现它，它似乎并不了解用=>缩短的功能。我替换了较长版本的缩短片段，但我没有得到相同的结果。

  var array = [[1,3,9]，[4,6,8]，[3,7,5]，[2,8,4]]; var sums = array.reduce（function （r，e，i）{e.forEach（function（a，j）{r [j] =（r [j] || 0）+ a; if（i == array.length-1）{r = r.map（function（el）{return el / array.length;}）;}}）; return r;}，[]）console.log（sums）;  

我没有看到这与缩短版本有什么区别，但这一个返回：

  sums = [0.15625，0.75，1.34375]; 
  

而不是：

  sums = [2.5，6，6.5]; 
  

总和是正确的，但是当我将el / array.length或者el / 4，结果是这3个奇怪的数字。我不明白那些来自哪里。你可以使用 reduce（）来解决这个问题。

和 forEach（）来返回结果。

  var array = [[1,3,9]，[4,6,8]，[3,7,5]，[2,8,4]]; var sums = array.reduce（函数（r，e，i）{e.forEach（（a，j）=> r [j] =（r [j] || 0）+ a）return r;}，[]）console.log总和） 

要计算每列的平均值，您可以添加<$

map（） -hide =falsedata-console =truedata-babel =false>

  var array = [[1,3,9]，[4,6,8]，[3,7,5]，[2,8,4]]; var sums = array.reduce（function （r，e，i）{e.forEach（（a， j）=> r [j] =（r [j] || 0）+ a）if（i == array.length  -  1）r = r.map（el => el / array.length）; 
  

I have an array that looks like this:

var array = [ [1,3,9],
              [4,6,8],
              [3,7,5],
              [2,8,4] ];

I want to get the average number of each column, but for now I was just trying to sum them. This is my code:

var sum = function(arr) {
  return arr.reduce(function(a, b) { return a + b; }, 0);
};

var tests = array.map(function(v, i) {
  return sum(array.map(function(v) { return v[i]; }))
});

return tests;

The output turns the sum correctly, but it seems to be doing as many sums as there are rows (4 rows), instead of 3 corresponding to the columns. This is the output:

tests = [10, 24, 26, NULL]

Any idea why is this happening? How can I perform the calculation only for as many columns as there are instead of rows?

EDIT:

I'm using Nenad's answer which gives the correct result. But I need to implement it on Google Sheets's Script Editor, which doesn't seem to understand the shortened functions with "=>". I replaced the shortened pieces for the longer version, but I'm not getting the same result.

var array = [ [1,3,9],
              [4,6,8],
              [3,7,5],
              [2,8,4] ];

var sums = array.reduce(function(r, e, i) {
    e.forEach(function(a,j) { r[j] = (r[j] || 0) + a;
                             if (i == array.length-1) { r = r.map(function(el){ return el/array.length; }); }
                            });
    return r;
  }, [])
  
console.log(sums);  

I don't see any difference between this and the shortened version, yet this one returns:

sums = [0.15625, 0.75, 1.34375];

Instead of:

sums = [2.5, 6, 6.5];

The sum is done correctly, but when I divide "el/array.length" or even "el/4", the result are these 3 weird numbers. I don't understand where are those coming from. Where did I go wrong?

解决方案

You can use reduce() and forEach() to return result.

var array = [
  [1, 3, 9],
  [4, 6, 8],
  [3, 7, 5],
  [2, 8, 4]
];

var sums = array.reduce(function(r, e, i) {
  e.forEach((a, j) => r[j] = (r[j] || 0) + a)
  return r;
}, [])

console.log(sums)

To calculate avg for each column you can add map() on last iteration of array.

var array = [
  [1, 3, 9],
  [4, 6, 8],
  [3, 7, 5],
  [2, 8, 4]
];

var sums = array.reduce(function(r, e, i) {
  e.forEach((a, j) => r[j] = (r[j] || 0) + a)
  if (i == array.length - 1) r = r.map(el => el / array.length);
  return r;
}, [])

console.log(sums)

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