Hi Carl, An example below; Rene Brun void binomial() { c1 = new TCanvas("c1","The FillRandom example",200,10,900,600); gaus1 = new TFormula("gaus1","gaus"); gaus1->SetParameters(1000,10,3); const int nbins = 20; h1 = new TH1F("h1","Test random numbers",nbins,0,20); h2 = new TH1F("h2","Test random numbers",nbins,0,20); h1->Sumw2(); h2->Sumw2(); h1->FillRandom("gaus1",8000); h2->FillRandom("gaus1",2000); TH1F *result = new TH1F("binomial","Test binomial",nbins,0,20); result->Divide(h1,h2,1.0,1.0,"b"); result->SetMarkerStyle(21); result->Draw(); } Carl Gwilliam wrote: > > Hi > > I want to plot a histogram with Binomial errors in the y direction, how > can I do this in root? > > More specifically I am dividing two histograms which plot Ntrig and N > as the height of each point to get the efficiency as: > > eff = Ntrig/N > > and on this divided histogram I want to plot the errors on each > point according to the formula: > > eff_error = sqrt(Ntrig/(N*N)*(1-Ntrig/N)). > > At the same time I want to plot the markers as points with x-error bars > which are the width of the bin. > > Cheers, > > Carl
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