Hi Rene,
why does h4 need the same number of bins? It is enough if h4 'takes' the
binning from either h3 or h2, isn't it?
Thomas.
Rene Brun wrote:
> Your two projections h2 and h3 have the same number of bins,
> eg you can do h3->Divide(h2);
> However, you call the default constructor for h4. h4 does not have the
> same number of bins as h2 and h3.
> Instead of
> TH2D *h4 = new TH2D;
> h4->Divide(h3, h2);
> do
> TH2D *h4 = (TH2D*)h2->Clone();
> h4->Divide(h3, h2);
>
> Rene Brun
>
> Thomas Bretz wrote:
>
>>Hi,
>>
>>I have a
>>Double_t x[5] = { 0, 1, 2, 3, 4 };
>>TH3D fHist("", "", 4, x, 4, x, 4, x);
>>and do:
>>fHist.GetZaxis()->SetRange(3, 4);
>>TH1 *h2 = fHist.Project3D("xy_off"); //, -1, 9999, "E");
>>
>>fHist.GetZaxis()->SetRange(1,2);
>>TH1 *h3 = fHist.Project3D("xy_on"); //, -1, 9999, "E");
>>
>>TH2D *h4 = new TH2D;
>>h4->Divide(h3, h2);
>>
>>And I get
>>Attempt to divide histograms with different number of bins...
>>
>>What am I doing wrong? I would expect to have two projections to have
>>the same binning...
>>
>>Thomas.
>
>
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