[ROOT] the commands on normalization doesn't work

From: tcli (tcli@ic.sunysb.edu)
Date: Thu Aug 07 2003 - 22:31:53 MEST 

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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