When I draw a histogram with the option “E0 P” on a log-y axis, I notice that the points for bins with zero entries in them are drawn on the bottom of the y-axis. Please see the example code below, which produced the attached file text.pdf.

test.pdf (15.9 KB)

The plot on the left, with a linear y-axis, behaves as expected. For bins with zero entries, the points are not visible, but the poisson error bars are visible. The plot on the right is a similar plot, but with a log y axis. The error bars are fine, but for some reason the points for empty bins are drawn, in this case at y=1, which is wrong. Is this a bug?

I am using root version 6.02/00

Thanks,

Emyr

[code]{

TCanvas *c1 = new TCanvas(“c1”,"",800,800);

c1->Divide(2);

TH1D * h1 = new TH1D(“h1”,“h1”,50,-4,4);

h1->SetMarkerStyle(21);

h1->FillRandom(“gaus”,100);

h1->SetBinErrorOption(TH1::kPoisson);

c1->cd(1);

h1->GetYaxis()->SetRangeUser(1,15);

h1->Draw(“E0 P”);

TH1D * h2 = new TH1D(“h2”,“h2”,50,-4,4);

h2->SetMarkerStyle(21);

h2->FillRandom(“gaus”,100);

h2->SetBinErrorOption(TH1::kPoisson);

c1->cd(2);

h2->GetYaxis()->SetRangeUser(1,15);

h2->Draw(“E0, P”);

gPad->SetLogy();

gPad->Update();

}[/code]