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Linear_regression.cpp

#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;

int main(){
    int n;
    cout << "Введите количество пар точек" << endl;
    cin >> n;
    double x[n], y[n], a, b;
    cout << "Введите значения абсцисс точек\n";
    for (int i=0; i<n; i++){
        cin >> x[i];
    }
    cout << "Введите значения ординат точек\n";
    for (int i=0; i<n; i++){
        cin >> y[i];
    }

    double xsum=0, x2sum=0, ysum=0, xysum=0;
    for (int i=0; i<n; i++){
        xsum += x[i]; //calculating sigma(x_i)
        ysum += y[i]; //calculating sigma(y_i)
        x2sum += pow(x[i],2); //calculating sigma(x^2_i)
        xysum += x[i]*y[i]; //calculating sigma(x_i * y_i)
    }

    a = (n*xysum - xsum*ysum)/(n*x2sum - xsum*xsum); //calculating the slope
    b = (x2sum*ysum - xsum*xysum)/(x2sum*n - xsum*xsum);

    double y_fit[n];
    for (int i=0; i<n; i++){
        y_fit[i] = a*x[i] + b;
    }
    cout << "S.no" << setw(5) << "x" << setw(19) << "y" << setw(19) << "y(fitted)" << endl;
    for (int i=0; i<n; i++){
        cout << i+1 << "." << setw(8) << x[i] << setw(15) << y[i] << setw(18) << y_fit[i] << endl;
    }
    cout << "\nУравнение найденной прямой\n" << a << "x + " << b << endl; //print the best fit line
    return 0;
}