用于计算5星级的算法

我需要像亚马逊网站上那样计算5星级。我已经进行了足够的搜索以找到最佳的算法，但是我找不到正确的答案。例如，如果这些是评分

5 star - 252
4 star - 124
3 star - 40
2 star - 29
1 star - 33

共478条点评

亚马逊计算得出这是“ 5星中的4.1星”。谁能告诉我这个数字是怎么得出的？我不能仅仅通过平均来得到这个。

这是一个加权平均值，您可以在其中将每个评分与其获得的票数进行权衡：

(5*252 + 4*124 + 3*40 + 2*29 + 1*33) / (252+124+40+29+33) = 4.11 and change

如果您从头开始计算总体评分，那么此公式将为您提供帮助。

式

((Overall Rating * Total Rating) + new Rating) / (Total Rating + 1)

例

假设您到目前为止没有评级，那么公式就像，到目前为止总评级是“ 0”。总评分为“ 0”，给定评分为“ 4”

((0*0)+4)/1 = 4

如果总评分为“ 4.11”，则总评分为“ 478”，而一位用户给出的新评分为“ 2”

那么公式就像

((4.11 * 478)+ 2)/479 // 479 is increment of new rating from 478

在evanmiller.org上，有关该主题的文章非常多。他仔细研究了几种方法的利弊，并提出了一种数学上可靠的加权和计票方法。

http://evanmiller.org/ranking-items-with-star-ratings.html

Blindy的回复非常有帮助，这是基于此的PHP代码。有些可能会有用。根据OP的示例，结果将为4.11：

$ratings = array(
5 => 252,
4 => 124,
3 => 40,
2 => 29,
1 => 33
);

function calcAverageRating($ratings) {

$totalWeight = 0;
$totalReviews = 0;

foreach ($ratings as $weight => $numberofReviews) {
    $WeightMultipliedByNumber = $weight * $numberofReviews;
    $totalWeight += $WeightMultipliedByNumber;
    $totalReviews += $numberofReviews;
}

//divide the total weight by total number of reviews
$averageRating = $totalWeight / $totalReviews;

return $averageRating;
}

如何构建上面的$ ratings数组

伪代码示例，但假设您有一个名为“ ratings”的表和一个名为“ rating”的列，则该伪代码应能解释在数据库中存储信息时如何构建$ ratings数组。在这种情况下，这是1次加入，您需要进行4次加入才能获得所有评分，但这应该可以帮助您入门：

SELECT count(c1.rating) as one_star, count(c2.rating) as two_star  
FROM ratings c1 
LEFT OUTER JOIN
ratings c2
ON
c1.id = c2.id
WHERE
c1.rating = 1
AND
c2.rating = 2

评论中建议的另一种方法

SELECT SUM(rating = 1) AS one_s ,SUM(rating = 2) AS two_s ,SUM(rating = 3) as three_s FROM reviews where product_id = 9

是的，您可以将它们平均化：

(5 * 252 + 4 * 124 + 3 * 40 + 2 * 29 + 1 * 33) / 478 = 4.11

一种更好的方法

rating = (sum_of_rating * 5)/sum_of_max_rating_of_user_count  

例：

total users rated: 6  
sum_of_max_rating_of_user_count: 6 x 5 = 30  
sum_of_rating: 25

rating = (25 * 5) / 30

做完了！

该评估系统基于加权平均值或加权平均值。也就是说，他们使用以星为单位的权重来计算一个四舍五入到4.1的十进制值。例如：

Sum of (weight * number of reviews at that weight) / total number of reviews
(5*252 + 4*124 + 3*40 + 2*29 + 1*33) / 478 = 4.1

加权平均值，将星星数乘以其权重，然后除以评论总数。

您可能需要检查一下该算法：使用PHP和MySQL以正确的方式计算平均评分-无需保存每个“星级”（也称为评分等级）及其对应的投票数，然后必须从表单中检索数千行每次需要计算数据库平均值时。（除非您想确切显示有多少人将1、2、3、4和5星评为给定项目）

根据您的问题，您的解决方案将是这样。

（Rate * TotalRatingOfThatRate）/ TotalNumberOfReviews之和

（（5 * 252）+（4 * 124）+（3 * 40）+（2 * 29）+（1 * 33））/（252 + 124 + 40 + 29 + 33）

输出将是4.1

（星级总数/评论总数* 5）* 5

=答案

将js中的小数固定为1。

answer.toFixed（1）;

范例5人的总评论是20星。

（20/5 * 5）* 5 = 4.0

用Java语言编写

function calcAverageRating(ratings) {

  let totalWeight = 0;
  let totalReviews = 0;

  ratings.forEach((rating) => {

    const weightMultipliedByNumber = rating.weight * rating.count;
    totalWeight += weightMultipliedByNumber;
    totalReviews += rating.count;
  });

  const averageRating = totalWeight / totalReviews;

  return averageRating.toFixed(2);
}


const ratings = [
  {
    weight: 5,
    count: 252
  },
  {
    weight: 4,
    count: 124
  },
  {
    weight: 3,
    count: 40
  },
  {
    weight: 2,
    count: 29
  },
  {
    weight: 1,
    count: 33
  }
];

console.log(calcAverageRating(ratings));

另外，我只是想为所有人编写实用而完整的代码。

我的Json对象数组

var yourRatingData =[{
        review_id:1,
        customer_id:5,
        customer_name:"Faysal",
        rating:5,
        review_content:"I like this product it's cool and best in quality"
    },
    {
        review_id:2,
        customer_id:6,
        customer_name:"Adams",
        rating:4,
        review_content:"It's quality product though price a bit high"
    },
    {
        review_id:3,
        customer_id:8,
        customer_name:"Jane",
        rating:3,
        review_content:"I like but should improve quality"
    },
    {
        review_id:4,
        customer_id:9,
        customer_name:"Julia",
        rating:1,
        review_content:"It's not good"
    }];

等级计算

let _5star = yourRatingData.filter(r=>r.rating==5).length;
let _4star = yourRatingData.filter(r=>r.rating==4).length;
let _3star = yourRatingData.filter(r=>r.rating==3).length;
let _2star = yourRatingData.filter(r=>r.rating==2).length;
let _1star = yourRatingData.filter(r=>r.rating==1).length;

//Sum of individual star.
let sumOfRating = parseInt( _5star + _4star + _3star + _2star + _1star );

//Total number of rating
let overallRating = parseInt( 5*_5star + 4*_4star + 3*_3star + 2*_2star +1*_1star );

//Average of all rating
let averageRating = parseFloat(overallRating/sumOfRating);

//Percentage of each star rating
let _5starPercentage = parseInt((_5star/totalRating)*100);
let _4starPercentage = parseInt((_4star/totalRating)*100);
let _3starPercentage = parseInt((_3star/totalRating)*100);
let _2starPercentage = parseInt((_2star/totalRating)*100);
let _1starPercentage = parseInt((_1star/totalRating)*100);

我认为这很有帮助。

与C＃

double rating = (double)(5 * star5 + 4 * star4 + 3 * star3 + 2 * star2 + 1 * star1) / (star1 + star2 + star3 + star4 + star5);
rating = Math.Round(rating, 1);