Hi Seng,
I have implemented your suggestion in the CVS version.
When a custom histogram is specified, the empty histogram will be drawn
even if the selection has generated 0 entries.
Rene Brun
Woon-Seng Choong wrote:
>
> I have an ntuple which contain variables var1, var2 and var3.
> Now, the selection
> ntuple->Draw("var1>>hist(256,-0.5,255.5)", "var2==0)
> gives zero entries. The question is why it draws nothing instead of an
> empty histogram. In addition
> (TH1F *)gPad->GetPrimitive("hist")
> gives a zero pointer. I know why it gives a zero pointer because the
> pad is empty. But it would be reasonable to get a pointer to a
> histogram with zero entries.
>
> Thank you
> Seng
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