// Hi brun,
//    this is a program to fit a 2D graph with legendre polynomial.
//    i have a problem.
//    you know, the function have 24 parameters, so i construct a 2F 
// function to fit it: 
//--------------- TF2 *f2=new TF2("fit",fit_f,4,150,0,180,24);
//    and fit :   f->Fit("fit","E");
//    the resule is only p0 and p1 is not zero.
// 	  But I found if i change TF2 into:
//---------------  TF2 *f2=new TF2("fit",fit_f,4,150,0,180,25);
// then fit it, i can get the result ,and the FCN is about 100.
//    I did not know why?








//---------this program is to draw  the 2D graph of en ,angle,cs ,cserror
//-------and fit them with legendre 

#include <TMath.h>
#include <TGraph2DErrors.h>
#include <TRandom.h>
#include <TStyle.h>
#include <TCanvas.h>
#include <TF2.h>
#include <TMultiGraph.h>
#include <iostream>
#include <TF1.h>


//----------first ,construct the function using to fit


//=====================================================================
//   the sub-function 0
Double_t fit_0(  Double_t *x, Double_t *par)
{
      Double_t fitval=par[0]*TMath::Exp(par[1]*x[1])+par[2]*TMath::Exp(par[3]*x[0])+(par[4]+par[5]*x[0])/(1+par[6]*(x[0]-par[7])*(x[0]-par[7]));
      return fitval;
 }


//====================================================================== 
//   the sub-function 1
Double_t  fit_1(  Double_t *x, Double_t *par) 
{
      Double_t fitval=(par[0]*TMath::Exp(par[1]*x[0])+par[2]*TMath::Exp(par[3]*x[0]))*ROOT::Math::assoc_legendre(1,0,cos(x[1]*TMath::Pi()/180));  
      return fitval;
}

//======================================================================
//   the sub-function 2
Double_t  fit_2(  Double_t *x, Double_t *par) 
{
      Double_t fitval=(par[0]*TMath::Exp(par[1]*x[0])+par[2]*TMath::Exp(par[3]*x[0]))*ROOT::Math::assoc_legendre(2,0,cos(x[1]*TMath::Pi()/180));  
      return fitval;
}

//======================================================================
//   the sub-function 3
Double_t  fit_3(  Double_t *x, Double_t *par) 
{
      Double_t fitval=(par[0]*TMath::Exp(par[1]*x[0])+par[2]*TMath::Exp(par[3]*x[0]))*ROOT::Math::assoc_legendre(3,0,cos(x[1]*TMath::Pi()/180));  
      return fitval;
}

//======================================================================
//   the sub-function 4
Double_t  fit_4(  Double_t *x, Double_t *par) 
{
      Double_t fitval=(par[0]*TMath::Exp(par[1]*x[0])+par[2]*TMath::Exp(par[3]*x[0]))*ROOT::Math::assoc_legendre(4,0,cos(x[1]*TMath::Pi()/180));  
                    
      return fitval;
}


//======================================================================
//sum of the fit function

Double_t fit_f( Double_t *x, Double_t *par)
{
    Double_t fitval=fit_3(x,&par[16])+fit_2(x,&par[12])+ fit_1(x,&par[8])+fit_0(x,par)+fit_4(x,&par[20]);
                  ;
               
    return fitval;
}



//==============================================================
//--------------------------------------------------------------

//            construct the main function 


//--------------------------------------------------------------
//==============================================================


void fit2Dg_of_diff()

{
   int counter=71;     // number of data point
	 Double_t en[71],angle[71],cs[71],cserror[71];
	 Double_t ex[71]={0.0};
	 Double_t ey[71]={0.0};
	 double zero;
	 int i;
	 
	 
	
	 gSystem->Load("libMathMore.dll");  
	 gStyle->SetOptFit(1111);
	 
	  
	  
	 
	 
	 // open the data file and read them
	 ifstream alldata("c:\\root\\3he\\all_normalize_data\\all_diff_data.txt");
	 if(!alldata)
	 	  cout<<"No file"<<endl;
	 
	 for(i=0;i<counter;i++){
	 
	    alldata>>en[i]>>angle[i]>>cs[i]>>zero>>cserror[i];
	    
	    cout<<en[i]<<"  "<<angle[i]<<"  "<<cs[i]<<"  "<<ex[i]<<" "<<cserror[i]<<endl;
	  }


//---------------------------------------

    TCanvas *c1 = new TCanvas("c1", "Fitting a 2DG ");  
	  TGraph2DErrors *f=new TGraph2DErrors(counter,en,angle,cs,ex,ey,cserror);
	    
	  f->Draw("P0 TRI1");
	  
	  
	  
	  
	  
	  //fit
	  
	 TF2 *f2=new TF2("fit",fit_f,4,150,0,180,25);
	  
	 f->Fit("fit","E");
	  
	  
	}