I have made a routine according to the MakeClass example. I read a Tree and then use the Loop() function to Fill a histogram of the selected TBranch. What I would like to do is to set a TCut when I Fill. I can of course do the TTree::Draw(…,TCut arguments, …), but for obvious reasons I dont want to use this routine. I couldn’t find any other function than the TTree::Draw function that accepts TCut objects as arguments. I couldnt put any TCut object into the Draw function for the TH1F.
Where do I set my TCut objects in this case?
the only way I can think of is a bit of a workaround. To test whether TTree* tree passes the TCut cut for entry number iEntry (so you can fill the histogram hist), run
if (tree->Draw("arbitrary tree var", cut, "goff", 1, iEntry))
myHist->Fill(...); As TTree::Draw returns the number of selected entries you can use it to test whether the current event passed your cuts.
For “simple” functions you can run tree->Draw(“arbitrary tree var>>myHist”, cut) outside the loop (i.e. on the whole tree). This will draw the “arbitrary tree var” into the histogram called myHist, using the TCut cut. See root.cern.ch/root/html/TTree#TTree:Draw for doc on how to specify the histogram which TTree::Draw should fill.