Question

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

Answer 1

import java.util.Arrays;

public class StatsCalculator {
    public static void main(String[] args) {
        double[] numbers = {3.4, 1.8, 4.3, 5.0, 6.2};

        double mean = calculateMean(numbers);
        double stddev = calculateStandardDeviation(numbers, mean);

        System.out.printf("Mean: %.2f%n", mean);
        System.out.printf("Standard Deviation: %.2f%n", stddev);
    }

    public static double calculateMean(double[] data) {
        if (data.length == 0) return 0.0;

        double sum = 0.0;
        for (double value : data) {
            sum += value;
        }
        
        return sum / data.length;
    }

    public static double calculateStandardDeviation(double[] data, double mean) {
        if (data.length < 2) return 0.0;

        double sumOfSquaredDifferences = 0.0;
        for (double value : data) {
            double diff = value - mean;
            sumOfSquaredDifferences += diff * diff;
        }

        double variance = sumOfSquaredDifferences / (data.length - 1);
        
        return Math.sqrt(variance);
    }
}



/*
run:

Mean: 4.14
Standard Deviation: 1.66

*/

 

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