René,
Rene Brun wrote:
> Use option "hist". See documentation of TH1::Draw, THistPainter::Paint
ummh ... is this an "automatic response" message ? of course I can use
"hist" (see the mail). the docs I'm reading them since 1997...
probably my mail was not clear enough ...
people usually expect doing h->Draw() and get something on the screen
(i.e. the default option="" of TH1::Draw to be "clever" enough to
display something) if the histo is not empty. I was asking perhaps for a
modification of THistPainter::Paint(Option_t *option) to plot, by
default (i.e. when option=""), the histo with "hist" option when the
errors are null ...
thanks
>> I want to plot (for graphical purposes only) a histogram which has
>> been filled manually and has null y-errors. The default drawing
>> option for histos in this case produces a "blank" output in the
>> canvas. An example shows the:
>>
>> TH1D* h = new TH1D("h","h",100,0,100);
>> h->FillRandom("pol1",5000);
>> h.Draw(); // no problem here the histo has non-null y-errors
>> for (int i=0;i<h->GetNbinsX()+1;i++){h->SetBinError(i,0.);};
>> h.Draw(); // the histo "disappears"
>> h.Draw("h"); // OK the histo is back there ...
>>
>> Is this is a bug or a feature ? Why doesn't THistPainter::Paint
>> (Option_t *option) set the default (empty) draw option to "h" in this
>> case ?
>>
>> Thanks.
>>
>> PS: Using root_v4.00.01.Linux.RH7.3.gcc296 binaries (same feature in
>> root_v3.10.01.Linux.RH7.3.gcc296)
>
--
David d'Enterria Nevis Labs, Columbia University
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