linear_regression.cpp

#include<bits/stdc++.h>
using namespace std;
bool custom_sort(double a, double b){
    double  a1=abs(a-0);
    double  b1=abs(b-0);
    return a1<b1;
}
int main()
{
//Intialization Phase//
double x1[] = {1, 2, 4, 3, 5,6,8,4,2,6,1,3};    // defining x values
double x2[] = {10,12,15,14,15,16,13,10,10,18,18,12};    // defining x values
double y[] = {1, 3, 3, 2, 5,4,2,5,6,1,4,8};    // defining y values
vector<double>error;             // array to store all error values
double err;
double b0 = 0;                   //initializing b0
double b1 = 0;                   //initializing b1
double b2 = 0;                   //initializing b1
double alpha = 0.01;             //intializing error rate

//Training Phase//
for (int i = 0; i < 20; i ++) {   // since there are 5 values and we want 4 epochs so run for loop for 20 times
    int idx = i % 5;              //for accessing index after every epoch
    double p = b0 + b1 * x1[idx] + b2 * x2[idx];  //calculating prediction
    err = p - y[idx];              // calculating error
    b0 = b0 - alpha * err;         // updating b0
    b1 = b1 - alpha * err * x1[idx];// updating b1
    b2 = b2 - alpha * err * x2[idx];// updating b1
    cout<<"B0="<<b0<<" "<<"B1="<<b1<<" "<<"B2"<<b2<<" "<<"error="<<err<<endl;// printing values after every updation
    error.push_back(err);
}
sort(error.begin(),error.end(),custom_sort);//sorting based on error values
cout<<"Final Values are: "<<"B0="<<b0<<" "<<"B1="<<b1<<" "<<"B2"<<b2<<" "<<"error="<<error[0]<<endl;

//Testing Phase//
cout<<"Enter a test x value";
double test1,test2;
cin>>test1>>test2;
double pred=b0+b1*test1+b2*test2;
cout<<endl;
cout<<"The value predicted by the model= "<<pred;
}