[ROOT] E-option and FitSlices

From: Dariusz Miskowiec (D.Miskowiec@gsi.de)
Date: Mon Nov 18 2002 - 15:45:22 MET


Dear Root experts,

I have the impression that performing a fit with option "E" 
affects not only the actual fit but also all fits which come 
after it. Particularly, FitSlices starts producing unreasonably 
small error bars for the second parameter. This is shown in 

http://www-linux.gsi.de/~misko/eoption.gif 

which was produced with root 3.03/09 under debian linux using 
enclosed macro. Many thanks and best regards

Dariusz Miskowiec

{
gROOT->Reset();
gStyle->SetPalette(1,0);

TF1 *ga1 = new TF1("ga1","gaus",-4,4);
TF2 *ga2 = new TF2("ga2","exp(-(y-200)*(y-200)/2/50/50)",-4,4,0,500);
ga1->SetParameters(100.0,0.0,1.0);
ga1->SetLineColor(2);

TH1F *his1 = new TH1F("his1","one dim",100,-4,4);
TH2F *his2 = new TH2F("his2","two dim",48,-4,4,50,0,500);
his1->FillRandom("ga1",1000);
his2->FillRandom("ga2",10000);

TCanvas *c1 = new TCanvas("c1","E-option problem",10,10,500,400);
c1->Divide(3,2);
 
c1->cd(1); his1->Fit("ga1");
c1->cd(2); his2->FitSlicesY();
c1->cd(2); his2->Draw("colz"); gROOT->Get("his2_1")->Draw("same");
c1->cd(3); gROOT->Get("his2_2")->Draw();

c1->cd(4); his1->Fit("ga1","E");
c1->cd(5); his2->FitSlicesY();
c1->cd(5); his2->Draw("colz"); gROOT->Get("his2_1")->Draw("same");
c1->cd(6); gROOT->Get("his2_2")->Draw();
}



-- 
+-----------------------------------------------------------------+
+  Dariusz Miskowiec                  E-mail: D.Miskowiec@gsi.de  +
+  GSI, Planckstr. 1                  Phone:  0049-6159-712-133   +
+  D-64291 Darmstadt                  Fax:    0049-6159-712-989   +
+-----------------------------------------------------------------+



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