Question

How to calculate the mean and the standard deviation of an array of floating-point values in JavaScript

Answer 1

function calculateMean(data) {
    if (data.length === 0) return 0.0;

    let sum = 0.0;
    for (let value of data) {
        sum += value;
    }

    return sum / data.length;
}

function calculateStandardDeviation(data, mean) {
    if (data.length < 2) return 0.0;

    let sumOfSquaredDiffs = 0.0;
    for (let value of data) {
        let diff = value - mean;
        sumOfSquaredDiffs += diff * diff;
    }

    let variance = sumOfSquaredDiffs / (data.length - 1); 
    
    return Math.sqrt(variance);
}

const numbers = [3.4, 1.8, 4.3, 5.0, 6.2];
const mean = calculateMean(numbers);
const stddev = calculateStandardDeviation(numbers, mean);

console.log(`Mean: ${mean.toFixed(2)}`);
console.log(`Standard Deviation: ${stddev.toFixed(2)}`);



/*
run:

Mean: 4.14
Standard Deviation: 1.66

*/

 

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