#include <iostream>
#include <gsl/gsl_fit.h>
#include <cmath>

using std::cout;
using std::pow;
using std::sqrt;

// #include <fstream>
// #include <sstream>
// #include <string>
// #include <vector>

//using std::ifstream;
//using std::istringstream;
//using std::vector;
//using std::string;
//using std::stod;
//using std::copy;

int main()
{
    double x[] = {0.0, 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.25, 3.5, 3.75, 4.0, 4.25, 4.5, 4.75};
    double y[] = {1.5891700001638700, 1.2046979031630900, 2.598484110379440, 2.2043375760987900, 3.002229375836470, 2.928655222350250, 3.4769844321649000, 4.007335261529810, 4.534192485682100, 5.76185759925369, 6.41954394976063, 6.023919923933230, 7.443742735575060, 7.870686775946450, 8.022587710435350, 9.395420889477870, 9.948288024421440, 9.986332770533490, 9.694674681091840, 10.519384785632700};
    double sig[] = {0.5320185951347170, 0.45427229254919400, 0.5077027054798450, 0.5205826529502230, 0.4698090780151540, 0.4773624121076510, 0.5018787752525470, 0.4897362325985810, 0.49462141854510300, 0.5405394898833090, 0.4523449367708450, 0.48898047501417500, 0.5342659697011440, 0.4730380798563350, 0.4572104512757930, 0.49902577926821200, 0.530527413902035, 0.48969676619036700, 0.5443240285483060, 0.47616567472190800};
    
    //if saved file is existed
    /*
    string tmp;
    std::ifstream fin;
    fin.open("line.dat");
    
    vector<double> xv;
    vector<double> yv;
    vector<double> sigv;
    vector<string> sv;
    string sbf;
    
    while(!fin.eof())
    {
        getline(fin, tmp);
        if(tmp == "") {break;}
        istringstream ss(tmp);
        while(getline(ss,sbf,','))
        {
            sv.emplace_bacK();
        }
        sv.shrink_to_fit();
        
        xv.emplace_back(stod(sv[0]));
        yv.emplace_back(stod(sv[1]));
        sigv.emplace_back(stod(sv[2]));
        
        sv.clear();
        sv.shrink_to_fit();
    }
    xv.shrink_to_fit();
    yv.shrink_to_fit();
    sigv.shrink_to_fit();
    
    double x[xv.capacity()];
    double y[yv.capacity()];
    double sig[sig.capacity()];
    
    copy(xv.begin(), xv.end(), x);
    copy(yv.begin(), yv.end(), y);
    copy(sigv.begin(), sigv.end(), sig);
    */

    for(int i = 0; i < sizeof(sig)/sizeof(double); ++i)
    {
        sig[i] = 1/sig[i];
    }

    double a, b, cov00, cov01, cov11, chisq;
    gsl_fit_wlinear(x, 1, sig, 1, y, 1, sizeof(x)/sizeof(double), &b, &a, &cov00, &cov01, &cov11, &chisq);
    cout << "y = " << a << "x + "<< b << "\n";
}