Hi, h2->GetMean(); returns the mean value of teh histogram bins. To get the value of the parameter "Mean" (2nd parameter of teh fitted function), do: h2->GetFunction("gaus")->GetParameter(1); for more information, see Users Guide and documentation of TH1::Fit http://root.cern.ch/root/htmldoc/TH1.html#TH1:Fit see also examples in the tutorials, eg FittingDemo.C Rene Brun On Fri, 29 Aug 2003, ginn gin wrote: > Hi, > Thank you for the quick reply. I have changed it > and it works. Now I tried to do a gaussian fitting and > get the Mean value for the fit. When I do it as shown > below, it gives me the Mean value of the histo before > the fitting. It does not give the Mean value of > fitting. How can I get this fixed? > > Thanks, > > Ginn > > I use RH 8.0 and ROOT 3.05 > ================= Program =================== > { > Double_t ave; > Int_t i; > > TFile f("mpeak.root"); > TH1F *h2= new TH1F("h2","",50,0.,1000); > gStyle->SetOptFit(); > for( i=6480; i<6500; i++){ > ntuple->Draw("bpul>>h2",Form("btub==55611&&ctub==%d",i); > h2->Fit("gaus","R","same",0.,1000); > ave = h2->GetMean(); > cout<<" average : "<<ave<<endl; > } > } > --- Rene Brun <brun@pcbrun.cern.ch> wrote: > > Hi, > > > > Replace the line: > > > > ntuple->Draw("bpul>>h2","btub==55611&&ctub==i"); > > by > > > > > ntuple->Draw("bpul>>h2",Form("btub==55611&&ctub==%d",i)); > > > > Rene Brun > > > > On Wed, 27 Aug 2003, > > ginn gin wrote: > > > > > Hi, > > > I need to open a root file and look for > > histograms > > > and get the mean value of each histogram. One of > > the > > > cut is each time changing. I need to put this as i > > and > > > initialize i in a for loop. Then i is the one of > > the > > > value in ntuple->Draw(.....). When I gave ctub == > > 6480 > > > without for loop it works. With the for loop i > > need to > > > give values for i= 6480,6481 etc. If I run > > following > > > it complains about i. How can I get this fixed. > > Any > > > hint or help is appreciated. > > > > > > Thank you, > > > gin > > > =========Here is the program and what is wrong === > > > > > > { > > > Double_t ave; > > > Int_t i; > > > > > > TFile f("mpeak.root"); > > > TH1F *h2= new TH1F("h2","",50,0.,1000); > > > > > > for( i=6480; i<6500; i++){ > > > > > ntuple->Draw("bpul>>h2","btub==55611&&ctub==i"); > > > ave = h2->GetMean(); > > > cout<<" average : "<<ave<<endl; > > > } > > > } > > > > > > __________________________________ > > > Do you Yahoo!? > > > Yahoo! SiteBuilder - Free, easy-to-use web site > > design software > > > http://sitebuilder.yahoo.com > > > > > > > > __________________________________ > Do you Yahoo!? > Yahoo! SiteBuilder - Free, easy-to-use web site design software > http://sitebuilder.yahoo.com >
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