#include "TF1.h"
#include "TCanvas.h"
#include "TGraph.h"
#include "TFile.h"
#include "TTree.h"
#include "TLeaf.h"
#include "TH1F.h"
#include "TGraphErrors.h"
   
// This first bit is my attempt to make various structures available globally
TF1 *FTheta90;
//

TGraph *Gr_fTheta90;


TGraph *x0Theta90;
TGraph *x2Theta90;
TGraph *x4Theta90;
//
Double_t h1X0[5]; 
Double_t h1X2[5];
Double_t h1X4[5];
Double_t h2X0[5]; 
Double_t h2X2[5];
Double_t h2X4[5];
Double_t h3X0[5];
Double_t h3X2[5];
Double_t h3X4[5];
Double_t h4X0[5]; 
Double_t h4X2[5];
Double_t h4X4[5];
//
Int_t nlines;
//
Int_t n = 5;
Double_t phi[] = {0,45,90,135,180};
//
Double_t G2;
Double_t G4;
//


Double_t fTheta90(Double_t *x, Double_t *par) {
	G2=par[0];
	G4=par[1];

	return x0Theta90->Eval(x[0])+G2*x2Theta90->Eval(x[0])+G4*x4Theta90->Eval(x[0]);  //I have tried passing values both this way - via TGraph
	//Int_t i = x[0]/45;
	//return h1X0[i]+h1X2[i]+h1X4[i]; //and this way by reference to arrays
}

void Example_script(){
	TFile* file = TFile::Open( "PhiCanvas.root", "READ" );
	TCanvas * PhiCanvas = (TCanvas*)file->Get("PhiCanvas");
	PhiCanvas->Draw();
//
	TTree *TREE = new TTree("TREE","Xk values from XkDat file");
	nlines = TREE->ReadFile("Xk.txt","G:P:X0:X2:X4");
	
	printf(" found %d points\n",nlines);
//

	for (int i=0;i<nlines;i++) 
       {	
	TREE->GetEntry(i);
	if (i<5){
		h1X0[i] = TREE->GetLeaf("X0")->GetValue(0);
		h1X2[i] = TREE->GetLeaf("X2")->GetValue(0);
		h1X4[i] = TREE->GetLeaf("X4")->GetValue(0);
		}
	else if (i<10){
		h2X0[i-5] = TREE->GetLeaf("X0")->GetValue(0);
		h2X2[i-5] = TREE->GetLeaf("X2")->GetValue(0);
		h2X4[i-5] = TREE->GetLeaf("X4")->GetValue(0);
		}
	else if (i<15) {
		h3X0[i-10] = TREE->GetLeaf("X0")->GetValue(0);
		h3X2[i-10] = TREE->GetLeaf("X2")->GetValue(0);
		h3X4[i-10] = TREE->GetLeaf("X4")->GetValue(0);
		}
	else {
		h4X0[i-15] = TREE->GetLeaf("X0")->GetValue(0);
		h4X2[i-15] = TREE->GetLeaf("X2")->GetValue(0);
		h4X4[i-15] = TREE->GetLeaf("X4")->GetValue(0);
		}
	}

//
	x0Theta90 = new TGraph(n,phi,h1X0);
//
	TGraph * x0Theta135 = new TGraph(n,phi,h2X0);
//    
	TGraph * x0ThetaNeg115 = new TGraph(n,phi,h3X0);
 //  
	TGraph * x0ThetaZero = new TGraph(n,phi,h4X0);
//
	x2Theta90 = new TGraph(n,phi,h1X2);
//
	TGraph * x2Theta135 = new TGraph(n,phi,h2X2);
// 
	TGraph * x2ThetaNeg115 = new TGraph(n,phi,h3X2);
//
	TGraph * x2ThetaZero = new TGraph(n,phi,h4X2);
//
	x4Theta90 = new TGraph(n,phi,h1X4);
//
	TGraph * x4Theta135 = new TGraph(n,phi,h2X4);
//
	TGraph * x4ThetaNeg115 = new TGraph(n,phi,h3X4);
//
	TGraph * x4ThetaZero = new TGraph(n,phi,h4X4);
//    
	TVirtualPad * pad1 = PhiCanvas->cd(1);
	//also possible
	//TPad * pad1 = ((TPad*)PhiCanvas->GetListOfPrimitives()->At(0));
	if (pad1)
	{
		FTheta90 = new TF1("FTheta90",fTheta90,0,180,2);  // This is the bit I can't get!!!!!!!!
		FTheta90->SetParameters(1,1);
		
		//TGraph of the Pad is called "Graph" not very descriptive :)
		TGraphErrors * gr = (TGraphErrors*)pad1->FindObject("Graph");
		//another possible way
		//TGraphErrors * gr = (TGraphErrors*)pad1->GetListOfPrimitives()->At(2);
		if (gr)
		{
			gr->Fit(FTheta90);
		}
		else
		{
			cout << "no graph found" << endl;
		}
	}
//
}