This not really a root problem ... just propagation of errors. The peak P (par[0])) is related to area by A=P*sigma*sqrt(2pi) (no integral function needed!), so given error matrix on P and sigma it easy to compute error on A. ----- Original Message ----- From: "Ahmad" <ahmed_jamel@yahoo.com> To: <roottalk@pcroot.cern.ch> Cc: <ahmed1@rcf.rhic.bnl.gov> Sent: Friday, February 27, 2004 6:18 PM Subject: [ROOT] statistical error of Intergation > Dear Rooters, > > I am new to the list, and I have the following which I coud not figure out > how to do it under root. I'm fitting my J/psi peaks by a Gaussian function : > f=N*Exp[-(x-\bar{x})^2/2 sigma^2]. Then I utilized the function > Integral(min,max) to find the area or the number of counts under this fit. > . > . > . > n[j]->Fit("Gaus","R"); > G->SetParameters(par[0],par[1],par[2]); > float mean = par[1]; > float sigma = par[2]; > float mlo = mean-3.0*sigma; > float mhi = mean+3.0*sigma; > cout <<mean<<" and "<<sigma<<" and " <<mlo<<"and "<<mhi<<endl; > float binw = n[j]->GetBinWidth(1); > double COUNTS = G->Integral(mlo,mhi)/binw; > . > . > . > > > I need to know how to find the statistical error of the integral, i.e. "COUNTS" > in root. > > Thank you very much > > Ahmed. > > > > > > ===== > "EAST OR WEST, HOME IS BEST". > > Ahmed Al-Jamel > Physics Department(http://www.physics.nmsu.edu) > New Mexico State University > Box 30001, MSC 3D > Las Cruces, NM 88003-8001 > Tel (off): (505)-646-7614. > http://www.feynman.nmsu.edu > http://www.phenix.bnl.gov/phenix/WWW/publish/ahmed1/ > > __________________________________ > Do you Yahoo!? > Get better spam protection with Yahoo! Mail. > http://antispam.yahoo.com/tools
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