What is the process for determining the average rating of an array?

Question

What is the process for determining the average rating of an array?

Here is an array of data provided:

    const ratingData = [
        {name: 'St. Marys School', rating:5},
        {name: 'St. Zaviers School', rating:4},
        {name: 'St. Marys School', rating:3},
        {name: 'Rahul English Medium School', rating:2},
        {name: 'St. Francis High School', rating:3},
        {name: 'Rahul English Medium School', rating:1},
        {name: 'St. Francis High School', rating:4},
        {name: 'Mother Marys High School', rating:5}
    ];

My goal is to calculate the average rating for each school in this array. The challenge lies in dealing with duplicate entries, such as having multiple ratings for a single school like "St. Mary's School". How can I combine these entries and calculate the average rating effectively? I attempted using the map function, but it did not provide the desired outcome.

The expected output should resemble the following: (This is just an example)

const output = [
     { name: 'St. Marys School', averageRating: 4},
     { name: 'St. Zaviers School', averageRating: 4},
     { name: 'Rahul English Medium School', averageRating: 1.5},
     { name: 'St. Francis High School', averageRating: 3.5},
     { name: 'Mother Marys High School', averageRating: 5}
];

javascript arrays average

Answer 1

Answer №1

const schoolRatings = [
    {name: 'Sunshine Elementary', rating:4},
    {name: 'Rainbow Middle School', rating:3},
    {name: 'Sunshine Elementary', rating:5},
    {name: 'Golden Oak High School', rating:2},
    {name: 'Evergreen Junior High', rating:3},
    {name: 'Golden Oak High School', rating:1},
    {name: 'Evergreen Junior High', rating:4},
    {name: 'Moonlight High', rating:5}
];

let sumRatingData = {};

for (let entry of schoolRatings) {
    if (sumRatingData[entry.name]) {
        sumRatingData[entry.name].total = sumRatingData[entry.name].total + entry.rating;
        sumRatingData[entry.name].count++;
    } else {
        sumRatingData[entry.name] = {
            total: entry.rating,
            count: 1
        };
    }
}

console.log('Total Ratings Data: ' + JSON.stringify(sumRatingData));

let averageRatings = [];

for (let entry of Object.keys(sumRatingData)) {
    averageRatings.push({
        name: entry,
        rating: sumRatingData[entry].total / sumRatingData[entry].count
    });
}

console.log('Average Ratings Data: ' + JSON.stringify(averageRatings));

The total ratings data will be:

{
    "Sunshine Elementary": {
        "total": 9,
        "count": 2
    },
    "Rainbow Middle School": {
        "total": 3,
        "count": 1
    },
    "Golden Oak High School": {
        "total": 3,
        "count": 2
    },
    "Evergreen Junior High": {
        "total": 7,
        "count": 2
    },
    "Moonlight High": {
        "total": 5,
        "count": 1
    }
}

And the average ratings data will be:

[
    {
        "name": "Sunshine Elementary",
        "rating": 4.5
    },
    {
        "name": "Rainbow Middle School",
        "rating": 3
    },
    {
        "name": "Golden Oak High School",
        "rating": 1.5
    },
    {
        "name": "Evergreen Junior High",
        "rating": 3.5
    },
    {
        "name": "Moonlight High",
        "rating": 5
    }
]

Answer 2

const schoolRatings = [
    {name: 'Sunshine Elementary', rating:4},
    {name: 'Rainbow Middle School', rating:3},
    {name: 'Sunshine Elementary', rating:5},
    {name: 'Golden Oak High School', rating:2},
    {name: 'Evergreen Junior High', rating:3},
    {name: 'Golden Oak High School', rating:1},
    {name: 'Evergreen Junior High', rating:4},
    {name: 'Moonlight High', rating:5}
];

let sumRatingData = {};

for (let entry of schoolRatings) {
    if (sumRatingData[entry.name]) {
        sumRatingData[entry.name].total = sumRatingData[entry.name].total + entry.rating;
        sumRatingData[entry.name].count++;
    } else {
        sumRatingData[entry.name] = {
            total: entry.rating,
            count: 1
        };
    }
}

console.log('Total Ratings Data: ' + JSON.stringify(sumRatingData));

let averageRatings = [];

for (let entry of Object.keys(sumRatingData)) {
    averageRatings.push({
        name: entry,
        rating: sumRatingData[entry].total / sumRatingData[entry].count
    });
}

console.log('Average Ratings Data: ' + JSON.stringify(averageRatings));

The total ratings data will be:

{
    "Sunshine Elementary": {
        "total": 9,
        "count": 2
    },
    "Rainbow Middle School": {
        "total": 3,
        "count": 1
    },
    "Golden Oak High School": {
        "total": 3,
        "count": 2
    },
    "Evergreen Junior High": {
        "total": 7,
        "count": 2
    },
    "Moonlight High": {
        "total": 5,
        "count": 1
    }
}

And the average ratings data will be:

[
    {
        "name": "Sunshine Elementary",
        "rating": 4.5
    },
    {
        "name": "Rainbow Middle School",
        "rating": 3
    },
    {
        "name": "Golden Oak High School",
        "rating": 1.5
    },
    {
        "name": "Evergreen Junior High",
        "rating": 3.5
    },
    {
        "name": "Moonlight High",
        "rating": 5
    }
]

Answer 3

Answer №2

Illustrated below is a sample scenario utilizing the reduce() function together with a Map to identify duplicate entries.

The initial step involves reducing the original array into a Map that stores the ratings of repeated entries in an array format.

{
{'Sunset High School': [4, 3, 1]},
{'Riverside Academy': [5]},
...
}

Subsequently, we transform this populated Map back into an array using Array.from, and then calculate the average rating by reducing the array of ratings.

const ratingData = [
    {name: 'Sunset High School', rating:4},
    {name: 'Riverside Academy', rating:5},
    {name: 'Sunset High School', rating:3},
    {name: 'Lakeview Middle School', rating:2},
    {name: 'Brighton Junior High', rating:3},
    {name: 'Lakeview Middle School', rating:1},
    {name: 'Brighton Junior High', rating:4},
    {name: 'Green Valley Elementary', rating:5},
    {name: 'Sunset High School', rating:1}
    ]
    
const mapData = ratingData.reduce((acc, {name, rating}) => {
  const match = acc.get(name);
  match ? 
  match.push(rating) :
  acc.set(name, [rating]);
  return acc;
}, new Map);

const averageArray = Array.from(mapData, ([name, ratings]) => {
  const rating = ratings.reduce((a, r) => (a + r))/ratings.length;
  return { name, rating }
});

console.log(averageArray);

Answer 4

Illustrated below is a sample scenario utilizing the reduce() function together with a Map to identify duplicate entries.

The initial step involves reducing the original array into a Map that stores the ratings of repeated entries in an array format.

{
{'Sunset High School': [4, 3, 1]},
{'Riverside Academy': [5]},
...
}

Subsequently, we transform this populated Map back into an array using Array.from, and then calculate the average rating by reducing the array of ratings.

const ratingData = [
    {name: 'Sunset High School', rating:4},
    {name: 'Riverside Academy', rating:5},
    {name: 'Sunset High School', rating:3},
    {name: 'Lakeview Middle School', rating:2},
    {name: 'Brighton Junior High', rating:3},
    {name: 'Lakeview Middle School', rating:1},
    {name: 'Brighton Junior High', rating:4},
    {name: 'Green Valley Elementary', rating:5},
    {name: 'Sunset High School', rating:1}
    ]
    
const mapData = ratingData.reduce((acc, {name, rating}) => {
  const match = acc.get(name);
  match ? 
  match.push(rating) :
  acc.set(name, [rating]);
  return acc;
}, new Map);

const averageArray = Array.from(mapData, ([name, ratings]) => {
  const rating = ratings.reduce((a, r) => (a + r))/ratings.length;
  return { name, rating }
});

console.log(averageArray);

What is the process for determining the average rating of an array?

Answer №1

Answer №2

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