[ROOT] how to copy a histogram from 1 root file to another?

From: Ivan Glushkov (glushkov@mail.desy.de)
Date: Wed Oct 20 2004 - 15:51:58 MEST


So, what I want to do is to take some histogram, saved in a root file, 
and use it in my program, and save it in the new output file from my 
program.  Looks easy.  Here is my code:

int main(int argc, char* argv[])
TFile *flMC_file = new TFile("mc.root"); //the file in which I already 
have my histogram (h1dNN) stored
TFile* file = TFile::Open("data.root", "RECREATE");  // my output file
TH1D* h1dMC_NN = (TH1D*)flMC_file->Get("h1dNN");

And the histogram is not in the file (but all other histograms created 
later are there)

Do you have an idea what is the problem?

      Cheers, Ivan

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