main.cpp

// this is the library to print out and take in (input and output ) of user
#include <iostream>
// to store a dynamic array
#include <vector>
// this is used to remove this std::cout and use it like this cout
using namespace std;

class CalculateBeta {
private:
    int N;
    vector<double> X,Y;
    //X=[], Y=[]
public:
    // constructor
    CalculateBeta(int n) {
        N = n;
    }


    // method to add one pair of data
    // addData(1,2)  ==> X=[1],Y=[2]
    // addData(4,6)  ==> X=[1,4],Y=[2,6]
    // addData(10,20)  ==> X=[1,4,10],Y=[2,6,20]
    void addData(double x, double y) {
        X.push_back(x);
        Y.push_back(y);
    };
    double computeBeta() {
        double sumX = 0, sumY = 0, sumXY = 0, sumX2= 0;
// sumX --> (EXi)
// sumY --> (EYi)
// sumXY --> (EXiYi)
// sumX2 --> (EXi 2)
        for (int i = 0; i < N; i++) {
            sumX += X[i];
            sumY += Y[i];
            sumXY += X[i] * Y[i];
            sumX2 += X[i] * X[i];

            // x= [50,78,80,67] y=[7,98,200,65]
        }
        double numerator = sumXY - (sumX * sumY) /N;
        double denominator = sumX2 - (sumX * sumX) /N;
        return numerator / denominator;
    }
};

int main() {
int n;
    cout << "Please number of pairs (n) you would want to take in: ";
    cin >> n;

    CalculateBeta calculate_beta(n);
    // Car ferrari()
    // ferrari.speed()

    // class is like creating a blueprint for an system, something a car can be a class.
    // we can create a class that is called Car can create method

    cout <<"Enter "<< n << " pairs (Xi Yi):"<< endl;
    for (int i = 0; i < n; i++) {

        double x, y;
        cout << "X" << (i+1) << ": ";
        cin >> x;
        cout << "Y" << (i+1) << ": ";
        cin >> y;
        calculate_beta.addData(x, y);
    }
    // x= [50,78,80,67] y=[7,98,200,65]
    cout << "Beta = " << calculate_beta.computeBeta() << endl;


    return 0;
};