// This macro demonstrates how to use combination of functions (TF1) if the
// functions are defined as a normal C++ functions.
// The components Osz and Pol are constructed with a global pointer
// pointing to it.
// these pointers are used in the Sumf 
//
// Author: Otto.Schaile@LMU.DE

#include "TCanvas.h"
#include "TF1.h"
#include "TMath.h"
#include "Riostream.h"

TF1 * wave = 0;      // global pointers to be used in sum functions
TF1 * line = 0;

Double_t Osz(Double_t *x, Double_t *par)

{
   Double_t amplitude  = par[0];   // use meaningful names
   Double_t omega = par[1];        // to improve readability
   Double_t phase= par[2];

   Double_t  xa = x[0];

   Double_t pi = TMath::Pi();
   return  amplitude * TMath::Cos(pi * omega * xa + phase);
};

//____________________________________________________________________

Double_t Pol(Double_t *x, Double_t *par)

{
   Double_t constant  = par[0];     // use meaningful names
   Double_t slope     = par[1];     // to improve readability

   Double_t  xa = x[0];
   
   return (constant + slope * xa);
};

//____________________________________________________________________

Double_t SumF (Double_t *x, Double_t *par)
{
   Double_t  ca = x[0];

   return (wave->Eval(ca) + line->Eval(ca));   
} 
//____________________________________________________________________

void drawit(){

//   TCanvas * c1 = new TCanvas("csum","Sum of functions",
//                            800,50,700,400);
//   use 100, 100 for icons (gif)
   TCanvas * c1 = new TCanvas("csum","Sum of functions",
                            800,50,100,100);
   c1->SetGridx();
   c1->SetGridy();
   c1->GetFrame()->SetLineWidth(4);
   c1->SetBottomMargin(0.2);
//  define range
   Double_t from = 0; 
   Double_t to   = 4;

   Double_t amplitude  = 4;  
   Double_t omega      = 1;
   Double_t phase      = 0;
//   Double_t phase      = 0.25 * TMath::Pi();

   wave = new TF1("wave",Osz,from,to, 3);
   wave->SetParameter(0, amplitude);
   wave->SetParameter(1, omega);
   wave->SetParameter(2, phase);

   Double_t constant = 0;
   Double_t slope    = 3;

   line = new TF1("ef1",Pol,from,to, 2);
   line->SetParameter(0, constant);
   line->SetParameter(1, slope);

   TF1 * sum  = new TF1("sum",SumF,from,to, 3);

   sum->SetMinimum(-5);
   sum->SetMaximum(20);
   sum->Draw();
   TAxis *xaxis = sum->GetHistogram()->GetXaxis();
   TAxis *yaxis = sum->GetHistogram()->GetYaxis();
   yaxis->SetTitle("Amplitude");
   yaxis->CenterTitle();
   yaxis->SetLabelSize(0.06);
   yaxis->SetTitleOffset(0.7);
   yaxis->SetTitleSize(0.06);

   xaxis->SetTitle("Angle[units of pi]");
   xaxis->CenterTitle();
   xaxis->SetLabelSize(0.06);
   xaxis->SetTitleOffset(1);
   xaxis->SetTitleSize(0.06);

   sum->SetLineColor(6);
   sum->SetLineWidth(2);

   wave->Draw("same");
   wave->SetLineColor(2);
   wave->SetLineWidth(2);

   line->Draw("same");
   line->SetLineColor(4);
   line->SetLineWidth(2);
   c1->Modified(kTRUE);
};