root/html/Background__decr_8C.html

void Background_decr() {
   Int_t i;
   const Int_t nbins = 1024;
   Double_t xmin     = 0;
   Double_t xmax     = nbins;
   Double_t source[nbins];
   gROOT->ForceStyle();
   TH1F *d    = new TH1F("d","",nbins,xmin,xmax);
   TString dir  = gROOT->GetTutorialDir();
   TString file = dir+"/spectrum/TSpectrum.root";
   TFile *f     = new TFile(file.Data());
   TH1F *back = (TH1F*) f->Get("back1");
   back->SetTitle("Estimation of background with decreasing window");
   back->GetXaxis()->SetRange(1,nbins);
   back->Draw("L");
   TSpectrum *s = new TSpectrum();
   for (i = 0; i < nbins; i++) source[i]=back->GetBinContent(i + 1);
   // Estimate the background
   s->Background(source,nbins,6,TSpectrum::kBackDecreasingWindow,
                 TSpectrum::kBackOrder2,kFALSE,
                 TSpectrum::kBackSmoothing3,kFALSE);
   // Draw the estimated background
   for (i = 0; i < nbins; i++) d->SetBinContent(i + 1,source[i]);
   d->SetLineColor(kRed);
   d->Draw("SAME L");
}