/**

    @file DetermDriftCorr.cpp
    @author Brian Magill
    @creationdate 8/8/2006
    
    
*/     


#include "DetermDriftCorr.h"
#include "Interp_Funct.h"
#include <vector>
#include <cmath>
#include <cassert>
#include <stdexcept>
#include <string>

using namespace std;

DetermDriftCorr::DetermDriftCorr(valarray<double> const &time, 
                                            valarray<double> const &signal)
    {
    
    string strErr;
    unsigned long i;
    
    double cov00; 
    double cov01; 
    double cov11; 
    double sumsq;

    vector<double> tim;            
    vector<double> V;  

    double intercept;
    double m_slope;
    long n = signal.size();
        
    assert(time.size() ==  signal.size() );          

    Vref = signal.sum()/signal.size();
    tref = time.sum()/time.size();
    
    for(i = 0; i < signal.size(); i++)
        {          
         tim.push_back(time[i]);
         V.push_back(Vref/signal[i]);
         }       

              
    if (linear_fit(&tim[0], &V[0], n, &intercept, &m_slope, &cov00, 
                                           &cov01, &cov11, &sumsq) != 0)
        {
        strErr = "DetermDriftCorr():Error occurred in calculating drift";
        throw runtime_error(strErr);        
        }
        
    slope           = m_slope;
    slopeError      = sqrt(cov11);

    hasData = true;
                    
    }