Hi Rooters, I was trying to fit a histogram with a gaussian+landau. My intention was as follows. The histogram ranges from -20 to 200. I want to fit the range from -20 to 10 with a gaussian and from 10 to 200 with a landau. Then I add the two fitting functions (gaus+landau) to fit the overall distribution. Here comes my problem I want the overall fit (which from now on we call "total") to follow a gaussian shape between -20 and 10 and then a landau shape between 10 and 200. But instead what I get is a continuous fitting shape (with no dip at 10 and no bump at 15, where the MPV of the landau is). I was following the "How to fit in a sub-range of an histogram" from the ROOT tutorial. I would appreciate if someone could kindly point me where I am doing wrong (or should I try some other procedure as $ROOTSYS/tutorials/FittingDemo.C where I define my own function). I am attaching the code I used (which is really $ROOTSYS/tutorials/multifit.C) //************************* TFile *f = new TFile("ADC_final.root"); adc_high_cent4 = (TH1F*)f->Get("adc_high_cent4"); g2 = new TF1("g2","landau",10,200); g1 = new TF1("g1","gaus",-20,10); total = new TF1("total","landau(0)+gaus(0)",-20,200); total->SetLineColor(2); g1->SetLineColor(4); adc_high_cent4->Fit("g1","R0"); g1->GetParameters(&par[0]); adc_high_cent4->Fit("g2","R0+"); g2->GetParameters(&par[3]); total->SetParameters(par); adc_high_cent4->Fit("total","R0+"); adc_high_cent4->Draw(); g1->Draw("same"); g2->Draw("same"); total->Draw("same"); //************************* Best Regards, -tahsina ----------------------------------------------------------------------------- Tahsina Ferdousi ------------------------------------------------------------------------------ Graduate Student |email: |Phone: Department of Physics |tahsina@phyun0.ucr.edu |(909)-787-7301 University of California |tahsina@ucrhi2.ucr.edu | Riverside, CA 92521 |url: | USA |www.phenix.bnl.gov/~tahsina| ------------------------------------------------------------------------------
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