用于计算五星评级的算法

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Yes, you can average them out:

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

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最佳答案

That's a weighted average, where you weigh each rating with the number of votes it got:

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

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This rating system is based on a weighted average or weighted mean. That is, they used the weight in terms of stars to compute a decimal value which rounds to 4.1. For example:

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

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Weighted average, sum the number of stars times its weight, and then divide it through by the total number of reviews.

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If you are start calculation of overall rating from beginning then this formula will help you.

Formula

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

Example

suppose you have no ratings till now then formula is like, overall rating is "0" till now. total rating "0" and given rating is "4"

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

If overall rating is "4.11" Total rating is "478" And new rating giving by one user is "2"

then formula is like

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

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Super helpful reply by Blindy, here's the PHP code that's based on it. Some may find useful. The results will be 4.11 as per OP's example:

$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;
}

How to build the above $ratings array

Example pseudo code, but which should work that explains how to build the $ratings array when info is stored in DB assuming you have a table called "ratings" and a column called "rating". In this case it's 1 join, you would need to do 4 joins to get all ratings, but this should get you started:

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

another approach suggested in comments

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

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a better way to do this,

rating = (sum_of_rating * 5)/sum_of_max_rating_of_user_count

example:

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


rating = (25 * 5) / 30

Done!

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in Javascript

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));

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(Total nunber of star / total number of persons who review * 5 ) * 5

= Answer

Fixed decimals in js to 1.

answer.toFixed(1);

Example the total reviews of 5 person is 20 star.

(20/5*5)*5 = 4.0

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According to your question your solution will be like this.

Sum of (Rate*TotalRatingOfThatRate)/ TotalNumberOfReviews


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

output will be 4.1

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In addition, I am just trying to make practical and full code for all.

My Json Object Array

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"
}];

Rating Calculation

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);

I think it's helpful.

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This is an example method using flutter,

double starRating = 5.0;
getRating() {
// ! Check Already Accepted by others or Not -----------------------------------
//
int totalof5s = 0;
int totalof4s = 0;
int totalof3s = 0;
int totalof2s = 0;
int totalof1s = 0;
//
FirebaseFirestore.instance
.collection('usersRating')
.where("passengerUid", isEqualTo: "GNblJJJsjicaA2vkXJNJ6XCAiwa2")
.snapshots()
.forEach((querySnapshot) {
if (querySnapshot.size > 0) {
querySnapshot.docs.forEach((element) async {
if (element["rating"] == 5) {
totalof5s++;
} else if (element["rating"] == 4) {
totalof4s++;
} else if (element["rating"] == 3) {
totalof3s++;
} else if (element["rating"] == 2) {
totalof2s++;
} else if (element["rating"] == 1) {
totalof1s++;
}
//
if (this.mounted) {
setState(() {
starRating = (5 * totalof5s +
4 * totalof4s +
3 * totalof3s +
2 * totalof2s +
1 * totalof1s) /
(totalof5s + totalof4s + totalof3s + totalof2s + totalof1s);
});
}
});
        

} else {
// This is default one in any case these user doesn't have any rating document exists
if (this.mounted) {
setState(() {
starRating = 5.0;
});
}
}
});
}