Hi Thomas, I suggest to use a variable bin size histogram as shown in the example below. Rene Brun void logaxis() { const Int_t nbins = 100; Double_t xmin = 1e-3; Double_t xmax = 1e3; Double_t logxmin = TMath::log10(xmin); Double_t logxmax = TMath::log10(xmax); Double_t binwidth = (logxmax-logxmin)/nbins; Double_t xbins[nbins+1]; xbins[0] = xmin; for (Int_t i=1;i<=nbins;i++) { xbins[i] = xmin + TMath::Power(10,logxmin+i*binwidth); } TH1F *h = new TH1F("h","hist with log x axis",nbins,xbins); Double_t x,xl; for (Int_t j=0;j<10000;j++) { xl = 0.5*(logxmin+logxmax) + 12*binwidth*gRandom->Gaus(0,1); x = xmin + TMath::Power(10,xl); h->Fill(x); } TCanvas *c1 = new TCanvas("c1"); c1->SetLogx(); h->Draw(); } Thomas Bretz wrote: > > Hello rooters, > > I have a histogram which is filled with some data. The get a more > conviniet view of the x-axis I set the bins of the histogram so, that if > I call gPad->SetLogx() I get equidistant bins. Now I want to fit this > view with a gaussian, but TH1::Fit fits the original data instead of the > logarithmic data. > > Is it possible to get either the nice view of a log-scaled X-Axis if i > would use equidistant bins and fill the histogram with log(data) or is > it possible to tell the fitter, that it should fit the logarithmic data > instead of the 'real' data in the histogram? > > Thanks, > Thomas.
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