Tips for calculating the average of various items within an array

Question

Tips for calculating the average of various items within an array

Hello everyone,

I'm currently facing a challenge in writing a JavaScript function that calculates the average values for an array of objects.

Below is the example array:

const array = [
      {
        createdAt: "2021-06-05",
        value: 0.2
      },
      {
        createdAt: "2021-06-05",
        value: 0.2
      },
      ...
    ]

The desired output should be:

const newArray = [
{
    createdAt: "2021-06-05",
    value: 0.467
  },
  ...
]

I attempted to use array.map on CodePen but encountered some issues, as shown in this example.

If you have any suggestions or solutions, I would greatly appreciate it!

javascript arrays

Answer 1

Answer №1

Map function does not alter the length of the resulting array and therefore is not suitable for this task. You will need to utilize Reduce to restructure the data accordingly.

This problem can be broken down into 2 separate tasks:

Grouping items by a specific key (in this case, the creation date)
Calculating the average within each group

The code provided may not be the most concise, but it effectively clarifies the process and produces the desired results.

const array = JSON.parse(`[{\"createdAt\":\"2021-06-05\",\"value\":0.2},{\"createdAt\":\"2021-06-05\",\"value\":0.2},{\"createdAt\":\"2021-06-05\",\"value\":1},{\"createdAt\":\"2021-06-06\",\"value\":0.2},{\"createdAt\":\"2021-06-06\",\"value\":0.3},{\"createdAt\":\"2021-06-06\",\"value\":0.8},{\"createdAt\":\"2021-06-07\",\"value\":0.7},{\"createdAt\":\"2021-06-07\",\"value\":0.7},{\"createdAt\":\"2021-06-08\",\"value\":0.7},{\"createdAt\":\"2021-06-08\",\"value\":0.2},{\"createdAt\":\"2021-06-08\",\"value\":0.9}]`)


function calculateAverageByDate(data) {
  const groups = data.reduce((map, record) => {
    const { createdAt, value } = record;
    
    if (map.has(createdAt)) {
      map.set(createdAt, map.get(createdAt).concat(value));
    } else {
      map.set(createdAt, [value])
    }
    
    return map
  }, new Map())
  
  const averages = [...groups.entries()].map(([createdAt, values]) => {
    return {
      createdAt,
      value: values.reduce((a, b) => a + b)/values.length
    }
  })
  
  return averages
}

console.log(JSON.stringify(calculateAverageByDate(array)))

Answer 2

Map function does not alter the length of the resulting array and therefore is not suitable for this task. You will need to utilize Reduce to restructure the data accordingly.

This problem can be broken down into 2 separate tasks:

Grouping items by a specific key (in this case, the creation date)
Calculating the average within each group

The code provided may not be the most concise, but it effectively clarifies the process and produces the desired results.

const array = JSON.parse(`[{\"createdAt\":\"2021-06-05\",\"value\":0.2},{\"createdAt\":\"2021-06-05\",\"value\":0.2},{\"createdAt\":\"2021-06-05\",\"value\":1},{\"createdAt\":\"2021-06-06\",\"value\":0.2},{\"createdAt\":\"2021-06-06\",\"value\":0.3},{\"createdAt\":\"2021-06-06\",\"value\":0.8},{\"createdAt\":\"2021-06-07\",\"value\":0.7},{\"createdAt\":\"2021-06-07\",\"value\":0.7},{\"createdAt\":\"2021-06-08\",\"value\":0.7},{\"createdAt\":\"2021-06-08\",\"value\":0.2},{\"createdAt\":\"2021-06-08\",\"value\":0.9}]`)


function calculateAverageByDate(data) {
  const groups = data.reduce((map, record) => {
    const { createdAt, value } = record;
    
    if (map.has(createdAt)) {
      map.set(createdAt, map.get(createdAt).concat(value));
    } else {
      map.set(createdAt, [value])
    }
    
    return map
  }, new Map())
  
  const averages = [...groups.entries()].map(([createdAt, values]) => {
    return {
      createdAt,
      value: values.reduce((a, b) => a + b)/values.length
    }
  })
  
  return averages
}

console.log(JSON.stringify(calculateAverageByDate(array)))

Answer 3

Answer №2

const data = [
  {
    date: "2021-06-05",
    amount: 0.2
  },
  {
    date: "2021-06-05",
    amount: 0.2
  },
  {
    date: "2021-06-05",
    amount: 1
  },
  {
    date: "2021-06-06",
    amount: 0.2
  },
  {
    date: "2021-06-06",
    amount: 0.3
  },
  {
    date: "2021-06-06",
    amount: 0.8
  },
  {
    date: "2021-06-07",
    amount: 0.7
  },
  {
    date: "2021-06-07",
    amount: 0.7
  },
  {
    date: "2021-06-08",
    amount: 0.7
  },
  {
    date: "2021-06-08",
    amount: 0.2
  }, 
  {
    date: "2021-06-08",
    amount: 0.9  
  }
]

let groupedData = data.reduce((grouped, {date, amount}) => ({
  ...grouped,
  [date]: grouped[date] 
                 ? [...grouped[date], amount] 
                 : [amount]
}), {})

let finalResult = Object.entries(groupedData).map(([date, amounts]) => ({
  date,
  amount: amounts.reduce((total, amount) => total + amount, 0) / amounts.length
}))

Answer 4

const data = [
  {
    date: "2021-06-05",
    amount: 0.2
  },
  {
    date: "2021-06-05",
    amount: 0.2
  },
  {
    date: "2021-06-05",
    amount: 1
  },
  {
    date: "2021-06-06",
    amount: 0.2
  },
  {
    date: "2021-06-06",
    amount: 0.3
  },
  {
    date: "2021-06-06",
    amount: 0.8
  },
  {
    date: "2021-06-07",
    amount: 0.7
  },
  {
    date: "2021-06-07",
    amount: 0.7
  },
  {
    date: "2021-06-08",
    amount: 0.7
  },
  {
    date: "2021-06-08",
    amount: 0.2
  }, 
  {
    date: "2021-06-08",
    amount: 0.9  
  }
]

let groupedData = data.reduce((grouped, {date, amount}) => ({
  ...grouped,
  [date]: grouped[date] 
                 ? [...grouped[date], amount] 
                 : [amount]
}), {})

let finalResult = Object.entries(groupedData).map(([date, amounts]) => ({
  date,
  amount: amounts.reduce((total, amount) => total + amount, 0) / amounts.length
}))

Answer 5

Answer №3

To start, create an object where the keys represent dates and the values are arrays of accumulated values for that date.

Utilize Object.entries along with map to generate an array of objects with average calculations.

const calculateAverage = (arr) => {
  const allValuesByDate = {};
  arr.forEach(({ createdAt, value }) => (allValuesByDate[createdAt] ??= []).push(value));
  return Object.entries(allValuesByDate).map(([createdAt, values]) => ({
    createdAt,
    avgValue: values.reduce((sum, val) => sum + val) / values.length,
  }));
};

const dataArray = [
  { createdAt: "2021-06-05", value: 0.2 },
  { createdAt: "2021-06-05", value: 0.2 },
  { createdAt: "2021-06-05", value: 1 },
  { createdAt: "2021-06-06", value: 0.2 },
  { createdAt: "2021-06-06", value: 0.3 },
  { createdAt: "2021-06-06", value: 0.8 },
  { createdAt: "2021-06-07", value: 0.7 },
  { createdAt: "2021-06-07", value: 0.7 },
  { createdAt: "2021-06-08", value: 0.7 },
  { createdAt: "2021-06-08", value: 0.2 },
  { createdAt: "2021-06-08", value: 0.9 },
];


console.log(calculateAverage(dataArray));

Answer 6

To start, create an object where the keys represent dates and the values are arrays of accumulated values for that date.

Utilize Object.entries along with map to generate an array of objects with average calculations.

const calculateAverage = (arr) => {
  const allValuesByDate = {};
  arr.forEach(({ createdAt, value }) => (allValuesByDate[createdAt] ??= []).push(value));
  return Object.entries(allValuesByDate).map(([createdAt, values]) => ({
    createdAt,
    avgValue: values.reduce((sum, val) => sum + val) / values.length,
  }));
};

const dataArray = [
  { createdAt: "2021-06-05", value: 0.2 },
  { createdAt: "2021-06-05", value: 0.2 },
  { createdAt: "2021-06-05", value: 1 },
  { createdAt: "2021-06-06", value: 0.2 },
  { createdAt: "2021-06-06", value: 0.3 },
  { createdAt: "2021-06-06", value: 0.8 },
  { createdAt: "2021-06-07", value: 0.7 },
  { createdAt: "2021-06-07", value: 0.7 },
  { createdAt: "2021-06-08", value: 0.7 },
  { createdAt: "2021-06-08", value: 0.2 },
  { createdAt: "2021-06-08", value: 0.9 },
];


console.log(calculateAverage(dataArray));

Tips for calculating the average of various items within an array

Answer №1

Answer №2

Answer №3

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