Finding Mean at Every Point in JavaScript Array

We have given the array of numbers and our task is to find the mean at every position in the array using JavaScript. Below we have added the example for a better understanding of the problem statement.

Example:

Input: arr = [1, 2, 3, 4, 5]
Output: 
Mean at position 1: 1
Mean at position 2: 1.5
Mean at position 3: 2
Mean at position 4: 2.5
Mean at position 5: 3
Explanation: 
Cumulative Sum: 1,  Mean: 1/1 = 1
Cumulative Sum: 1 + 2 = 3, Mean: 3/2 = 1.5
Cumulative Sum: 1 + 2 + 3 = 6, Mean: 6/3 = 2
Cumulative Sum: 1 + 2 + 3 + 4 = 10, Mean: 10/4 = 2.5
Cumulative Sum: 1 + 2 + 3 + 4 + 5 = 15, Mean: 15/5 = 3

We can find this mean using three different methods which are stated below:

Using JavaScript For Loop

In this approach, we are using the for loop to iterate over the input array and we are calculating the mean at each position and printing the mean at each point using the console.log function.

Example: In this example, we will find the mean at every point in JavaScript using For Loop.

const arr = [1, 2, 3, 4, 5];
let s = 0;
for (let i = 0; i < arr.length; i++) {
    s += arr[i];
    const res = s / (i + 1);
    console.log(`Mean at position ${i + 1}: ${res}`);
}

Mean at position 1: 1
Mean at position 2: 1.5
Mean at position 3: 2
Mean at position 4: 2.5
Mean at position 5: 3

Using the Array Map Method

In this method, we are using the map function wot compute the mean at each potion in the input array by updating the cumulative sum and storing the means in the means array.

Example: In this example, we will find the mean at every point in JavaScript using the Array Map Method

const arr = [5,4,3,2,1];
let s = 0;
const means = arr.map((value, index) => {
    s += value;
    const res = s / (index + 1);
    console.log(`Mean at position ${index + 1}: ${res}`);
    return res;
});

Mean at position 1: 5
Mean at position 2: 4.5
Mean at position 3: 4
Mean at position 4: 3.5
Mean at position 5: 3

Using the Array Reduce Method

In this method, we are using the reduce function to compute the mean at each potion in the array by updating the cumulative sum and storing the mean in the means array.

Example: In this example, we will find the mean at every point in JavaScript using the Array Reduce Method

const arr = [1, 2, 3, 4, 5];
const means = arr.reduce((acc, v, idx) => {
    const s = acc.sum + v;
    const res = s / (idx + 1);
    acc.means.push(res);
    console.log(`Mean at position ${idx + 1}: ${res}`);
    return { sum: s, means: acc.means };
}, { sum: 0, means: [] });

Mean at position 1: 1
Mean at position 2: 1.5
Mean at position 3: 2
Mean at position 4: 2.5
Mean at position 5: 3

Using a Generator Function

In this approach, we use a generator function to yield the mean at each position in the array. Generators are a special type of function that can be paused and resumed, making them suitable for iterating over sequences of values. This method allows for a clean and efficient way to compute the means without the need for additional storage.

Example:

function* calculateMean(arr) {
    let cumulativeSum = 0;
    
    for (let i = 0; i < arr.length; i++) {
        cumulativeSum += arr[i];
        yield cumulativeSum / (i + 1);
    }
}

const arr = [1, 2, 3, 4, 5];
const meanGenerator = calculateMean(arr);

for (let mean of meanGenerator) {
    console.log(`Mean at position ${arr.indexOf(mean) + 1}: ${mean}`);
}

Mean at position 1: 1
Mean at position 0: 1.5
Mean at position 2: 2
Mean at position 0: 2.5
Mean at position 3: 3

Method 4: Using a Functional Approach with Array.map() and Array.slice()

In this approach, we use the Array.map() method along with Array.slice() to create a new array containing the means at each position. We iteratively calculate the mean for each position by slicing the array from index 0 to the current position and then computing the sum and mean.

Example:

function calculateMeanUsingMap(arr) {
  return arr.map((_, index) => {
    const currentSlice = arr.slice(0, index + 1);
    const sum = currentSlice.reduce((acc, num) => acc + num, 0);
    return sum / currentSlice.length;
  });
}

const arr = [1, 2, 3, 4, 5];
const means = calculateMeanUsingMap(arr);

means.forEach((mean, index) => {
  console.log(`Mean at position ${index + 1}: ${mean}`);
});

Mean at position 1: 1
Mean at position 2: 1.5
Mean at position 3: 2
Mean at position 4: 2.5
Mean at position 5: 3