//Linear Fit
#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
int main()
{
int i,j,k,n;
cout<<"\nEnter the no. of data pairs to be entered:\n"; //To find the size of arrays
cin>>n;
double x[n],y[n],a,b;
cout<<"\nEnter the x-axis values:\n"; //Input x-values
for (i=0;i<n;i++)
cin>>x[i];
cout<<"\nEnter the y-axis values:\n"; //Input y-values
for (i=0;i<n;i++)
cin>>y[i];
double xsum=0,x2sum=0,ysum=0,xysum=0; //variables for sums/sigma of xi,yi,xi^2,xiyi etc
for (i=0;i<n;i++)
{
xsum=xsum+x[i]; //calculate sigma(xi)
ysum=ysum+y[i]; //calculate sigma(yi)
x2sum=x2sum+pow(x[i],2); //calculate sigma(x^2i)
xysum=xysum+x[i]*y[i]; //calculate sigma(xi*yi)
}
a=(n*xysum-xsum*ysum)/(n*x2sum-xsum*xsum); //calculate slope
b=(x2sum*ysum-xsum*xysum)/(x2sum*n-xsum*xsum); //calculate intercept
double y_fit[n]; //an array to store the new fitted values of y
for (i=0;i<n;i++)
y_fit[i]=a*x[i]+b; //to calculate y(fitted) at given x points
cout<<"S.no"<<setw(5)<<"x"<<setw(19)<<"y(observed)"<<setw(19)<<"y(fitted)"<<endl;
cout<<"-----------------------------------------------------------------\n";
for (i=0;i<n;i++)
cout<<i+1<<"."<<setw(8)<<x[i]<<setw(15)<<y[i]<<setw(18)<<y_fit[i]<<endl;//print a table of x,y(obs.) and y(fit.)
cout<<"\nThe linear fit line is of the form:\n\n"<<a<<"x + "<<b<<endl; //print the best fit line
return 0;
}

PhD researcher at Friedrich-Schiller University Jena, Germany. I'm a physicist specializing in theoretical, computational and experimental condensed matter physics. I like to develop Physics related apps and softwares from time to time. Can code in most of the popular languages. Like to share my knowledge in Physics and applications using this Blog and a YouTube channel.

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