[ROOT] last channel of variable bin size hist

From: Patrick SIZUN (sizun@discovery.saclay.cea.fr)
Date: Tue Feb 10 2004 - 18:18:22 MET 

Hi,

I face a problem when drawing a variable bin size histo in log scale.
The last channel is not displayed correctly but is much larger than it should.

Below is an example where I just took  a script given in the roottalk forum and 
changed the minimum to show the phenomenon.

Can some one help ?

P. Sizun

{
   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->SetMinimum(-200.0);
    h->Draw();
}

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