Hi Francesco, TTree::Draw cannot add two TLorentzVectors. I agree that this would be a nice feature to perform operations between vectors and then call a function on the final object. The only syntax that would work is: res->Draw("p4_pi1_eta_rec_fit.M() + p4_pi2_eta_rec_fit.M()") but, obviously, this is not what you want Rene Brun On 15 Jun 2004, Francesco Perfetto wrote: > Hi all, > > I would like add 2 or more TLorentzVector for then take the .M(). > After I open my root file with TBrowser in which there are the > TLorentzVector I do at command line: > > root [1] .L $ROOTSYS/lib/libPhysics.so > root [2] res->Draw("(p4_pi1_eta_rec_fit + p4_pi2_eta_rec_fit).M()") > > (WHERE p4_pi1_eta_rec_fit. and p4_pi2_eta_rec_fit. are 2 my > TLorentzVector) > > but I have the following error: > > *ERROR 30 : > Bad numerical expression :"(p4_pi1_eta_rec_fit+p4_pi2_eta_rec_fit).M()" > root [3] > > There is anyone that can help me? > > Thanks in advance. > Francesco. >
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