Hi,
Did you try :
Double_t scale = 1/h.GetSum();
h.Scale(scale);
Instead of :
Double_t scale = 1/h.Integral();
h.Scale(scale);
Martin
On Thu, 7 Aug 2003, tcli wrote:
> Dear root users,
> From the manual, the commands to normalize a histogram (TH1 *h)
> is:
> Double_t scale = norm/h.Integral();
> h.Scale(scale);
>
> I tried to normalize a histogram to 1, but that doesn't work. The
> normalized histo isn't drawn. And root doesn't say it's an error.
> However, if I want to include the two lines mentioned above in a macro,
> an error "Error: / Illegal operator for pointer 3 .....
> Error: non class,struct,union object 1/pt used with . or ->..." appears.
>
> My commands when I do it on the command line, not in the macro:
> root [] TH1F *nj = new TH1F("nj","NJET",100,0,20)
> root [] t.Draw("NJET>>nj") //NJET is a leave name in a tree
> root [] nj.Draw() //an un-normalized histo drawn
> root [] Double_t scale = 1/nj.Integral()
> root [] nj.Scale(scale)
> root [] nj.Draw() //still, an un-normalized histo
>
>
> When I try to go further to normalize it per entry and per unit of X
> axis. An error appears.
>
> My command:
> root [18] Double_t scale = nj.GetXaxis().GetBinWidth(1)/nj.GetIntegral()
> Error: operator '/' divided by zero FILE:(tmpfile) LINE:1
> *** Interpreter error recovered ***
>
> Any suggestions?
>
> Thanks in advance!
>
> tcli
>
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