Simple Linear Regression Implementation In Java

package com.rez.apps;

/*
    @author
	
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 */

interface RegresiLinierSederhana{
    void setData_prediktor(double[] dataPrediktor);
    void setData_response(double[] dataResponse);
    void setNilai_sigmaX();
    void setNilai_sigmaY();
    void setNilai_sigmaXY();
    void setNilai_sigmaX2();
    void setNilai_a();
    void setNilai_b();
    void setNilai_n(double n);
    void setNilai_X(double X);

    double getNilai_sigmaX();
    double getNilai_sigmaY();
    double getNilai_sigmaXY();
    double getNilai_sigmaX2();
    double getNilai_n();
    double getNilai_Y();
}

class estimasiJumlahMahasiswaLulus implements RegresiLinierSederhana{
    private double sigmaX, sigmaY, sigmaXY, sigmaX2, X, Y, a, b, n, dataPrediktor[], dataResponse[];

    @Override
    public void setNilai_sigmaX() {
        double tmp = 0;
        for (int i = 0; i < this.dataPrediktor.length; i++){
            tmp += dataPrediktor[i];
        }
        this.sigmaX = tmp;
    }

    @Override
    public void setNilai_sigmaY() {
        double tmp = 0;
        for (int i = 0; i < this.dataResponse.length; i++){
            tmp += dataResponse[i];
        }
        this.sigmaY = tmp;
    }

    @Override
    public void setNilai_sigmaXY() {
        double tmp[] = new double[dataPrediktor.length];
        double tmp2 = 0;
        for (int i = 0; i < this.dataPrediktor.length; i++){
            tmp[i] = dataPrediktor[i] * dataResponse[i];
        }
        for (int i = 0; i < this.dataPrediktor.length; i++){
            tmp2 += tmp[i];
        }
        this.sigmaXY = tmp2;
    }

    @Override
    public void setNilai_sigmaX2() {
        double tmp[] = new double[dataPrediktor.length];
        double tmp2 = 0;

        for (int i = 0; i < this.dataPrediktor.length; i++){
            tmp[i] += dataPrediktor[i] * dataPrediktor[i];
        }
        for (int i = 0; i < this.dataPrediktor.length; i++){
            tmp2 = tmp2 + tmp[i];
        }
        this.sigmaX2 = tmp2;
    }

    @Override
    public void setNilai_a() {
        this.a =( ( this.sigmaY * this.sigmaX2 ) - ( this.sigmaX * this.sigmaXY ) ) / ( ( this.n * this.sigmaX2 ) - ( this.sigmaX * this.sigmaX ) );
    }

    @Override
    public void setNilai_b() {
        this.b = ( ( this.n * this.sigmaXY ) - ( this.sigmaX * this.sigmaY ) ) / ( ( this.n * this.sigmaX2 ) - ( this.sigmaX * this.sigmaX ) );
    }

    @Override
    public void setNilai_n(double n) {
        this.n = n;
    }

    @Override
    public void setNilai_X(double X) {
        this.X = X;
    }

    @Override
    public void setData_prediktor(double[] dataPrediktor) {
        this.dataPrediktor = dataPrediktor;
    }

    @Override
    public void setData_response(double[] dataResponse) {
        this.dataResponse = dataResponse;
    }

    @Override
    public double getNilai_Y() {
        this.Y = this.a + ( this.b * this.X);
        return Y;
    }

    @Override
    public double getNilai_sigmaX() {
        return this.sigmaX;
    }
    @Override
    public double getNilai_sigmaY() {
        return this.sigmaY;
    }

    @Override
    public double getNilai_sigmaXY() {
        return this.sigmaXY;
    }

    @Override
    public double getNilai_sigmaX2() {
        return this.sigmaX2;
    }

    @Override
    public double getNilai_n() {
        return n;
    }

    protected int jumlahKelulusanMahasiswa(){
        return (int) this.getNilai_Y();
    }
}

public class Kelompok_3 {
    static int tahun = 2019;
    public static void main(String[] args) {


        double[] dataPrediktor = {
                1299,1208,1286,1352,1330,1337,1346,1328,1491,1424,1504,1544,1571,1598,1612 // Merupakan data jumlah mahasiswa masuk 15 tahun terakhir
        };

        double[] dataResponse = {
                869,997,1059,1080,1017,1044,1056,1165,1255,1126,1139,1179,1188,1204,1378 // Merupakan data jumlah mahasiswa lulus 15 tahun terakhir
        };

        int[] dataEstimasiMahasiswaMasuk = {
                1690,1521,1721,1782,1683    // Merupakan data Estimasi jumlah mahasiswa masuk 5 tahun yang akan datang. 2019 - 2023.
        };

        if (dataPrediktor.length != dataResponse.length){
            System.out.println("Estimasi tidak dapat dijalankan, mohon periksa kembali data anda");     // Jika jumlah data Prediktor dan Response tidak sama, estimasi tidak dijalankan
        }else{
            estimasiJumlahMahasiswaLulus tugas5 = new estimasiJumlahMahasiswaLulus();
            tugas5.setData_prediktor(dataPrediktor);
            tugas5.setData_response(dataResponse);
            tugas5.setNilai_n(dataPrediktor.length);
            tugas5.setNilai_sigmaX();
            tugas5.setNilai_sigmaY();
            tugas5.setNilai_sigmaXY();
            tugas5.setNilai_sigmaX2();
            tugas5.setNilai_a();
            tugas5.setNilai_b();

            for (int i = 0; i < dataEstimasiMahasiswaMasuk.length; i++){
                int tmp = tahun+i;
                tugas5.setNilai_X(dataEstimasiMahasiswaMasuk[i]);
                System.out.println("Estimasi Jumlah Mahasiswa Lulus Tahun "+ tmp +" berjumlah "+ tugas5.jumlahKelulusanMahasiswa() + " Mahasiswa ");
            }
        }
    }
}