How to Find the Variance of Numbers in 2D Array in C++?

// C++ Program to find the variance in a 2D array

#include <cmath>
#include <iostream>

using namespace std;

// Function to calculate the overall mean and variance of a
// 2D array
double calculateVariance(int rows, int cols,
                         int matrix[][3])
{
    double sum = 0;
    double squaredDiff = 0;
    int totalCount = rows * cols;

    // Calculate the sum of all elements
    for (int i = 0; i < rows; ++i) {
        for (int j = 0; j < cols; ++j) {
            sum += matrix[i][j];
        }
    }

    // Calculate the overall mean
    double overallMean = sum / totalCount;

    // Calculate the squared difference from the mean for
    // each element
    for (int i = 0; i < rows; ++i) {
        for (int j = 0; j < cols; ++j) {
            squaredDiff
                += pow(matrix[i][j] - overallMean, 2);
        }
    }

    // Calculate variance
    double variance = squaredDiff / totalCount;

    return variance;
}

int main()
{
    const int rows = 3;
    const int cols = 3;
    int matrix[rows][cols] = { { 10, 20, 30 },
                               { 40, 50, 60 },
                               { 70, 80, 90 } };

    double result = calculateVariance(rows, cols, matrix);
    cout << "Variance: " << result << endl;

    return 0;
}