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Re: Different results for same information extracted in different ways [message #17465 is a reply to message #17464] Fri, 07 November 2014 13:55 Go to previous messageGo to previous message
Klaus Götzen is currently offline  Klaus Götzen
Messages: 293
Registered: June 2006
Location: GSI
first-grade participant
From: *gsi.de
Hi Mamen,


concerning the discrepancy between the first two approaches (GetEntries() and summing the bin contents), I think a TH1 histogram in reality has n+2 bins, the n bins plotted and an overflow and underflow bin. Therefore you should actually try to loop like

int TotalEntries=0;
for (int i=0; i <Nbins+2;i++ )
{
  TotalEntries=TotalEntries+Reco->GetBinContent(i);// histograms start on bin=1 not bin=0
}
cout << "Total Reco Entries: "<< TotalEntries<< endl;


In the last case with the loop over the tree itself, I'm not sure. What I could imagine is, that e.g. the variable you set the branch address to has wrong type and then behaves unpredictable. I.e. check whether eppid really is a int branch and not a float branch. Of course you again don't count over- and underflow with this method.


Best,
Klaus
 
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