// root.cern.ch/root/htmldoc/guides/spectrum/Spectrum.html#dimensional-spectra
// root.cern.ch/doc/master/Background__incr_8C.html

// "The function allows to separate useless spectrum information 
// (continuous background) from peaks, based on Sensitive Nonlinear Iterative 
// Peak (SNIP) Clipping Algorithm. In fact, it represents the second order 
// difference filter (-1,2,-1)."

// See: M.Morhac et al., Nucl. Instr. Meth. A 401, 113 (1997)

// Example to illustrate the background estimator (class TSpectrum).
//
// Authors: Miroslav Morhac, Olivier Couet


void Background_incr () 
{
  Int_t i;
  Int_t nbins = 1024;
  Double_t  xmin     = 0;
  Double_t  xmax     = nbins;
  Double_t* source   = new Double_t [nbins];
  gROOT->ForceStyle();

  TFile* f     = new TFile ("TSpectrum.root");
  TH1F* hdata = (TH1F*) f->Get ("back1");
  hdata->SetTitle ("Estimation of background with increasing window");
  hdata->GetXaxis()->SetRange (1, nbins);
  hdata->Draw ("L");

  TSpectrum* Analyser1dim = new TSpectrum ();

  for (i = 0; i < nbins; i++) source[i] = hdata->GetBinContent (i+1);

  // Estimate the Background

  Analyser1dim->Background (
           source, nbins, 6, TSpectrum::kBackIncreasingWindow,
           TSpectrum::kBackOrder2, kFALSE,
           TSpectrum::kBackSmoothing3, kFALSE);

/*
    const char* TSpectrum::Background (
     Double_t* spectrum,      pointer to the vector of source spectrum
     Int_t ssize,	      length of the spectrum vector
     Int_t numberIterations,  maximal width of clipping window,
     Int_t direction,	      direction of change of clipping window. 
			      Possible values: kBackIncreasingWindow, kBackDecreasingWindow
     Int_t filterOrder,	      order of clipping filter. Possible values:
			      kBackOrder2, kBackOrder4, kBackOrder6, kBackOrder8
     bool  smoothing,	      logical variable whether the smoothing operation in the
			      estimation of background will be included. (0/1)
     Int_t smoothWindow,      width of smoothing window. Possible values: 
			      kBackSmoothing3, kBackSmoothing5, ..., kBackSmoothing15
     bool  compton	      whether the estimation of Compton edge will be included. (0/1)
   ) 

   See: root.cern.ch/doc/v608/classTSpectrum.html#a7830480612d1ee301964e6c79319f444
*/



  // Draw the estimated background

  TH1F* hbkgnd = new TH1F ("hbkgnd", "", nbins, xmin, xmax);
  for (i = 0; i < nbins; i++) hbkgnd->SetBinContent (i+1, source[i]);
  hbkgnd->SetLineColor (kRed);
  hbkgnd->Draw ("SAME L");
}