Hi Miro, You can do something like: tree.Draw("varx:vary","selection","goff",0); then use the result of the TTreeFormula objects created above tree->GetVar1,2,3, etc Rene Brun On Mon, 24 Jun 2002, Miroslav Helbich wrote: > > Hi all and developers, > > is there any way to figure out if the variable expression and data > selection string are O.K. in > > TTree::Draw(const char* varexp, char* selection, Option_t* option, Int_t > nentries= 1000000000, Int_t firstentry = 0) > > and what dimensional histogram is going to be drawn? > > I am sometimes writing the classes which pass this arguments > from user (or are created inside the code). Is there any way to figure out > if this will perform O.K. before passing this to the TTree::Draw()? > > There must be some parsing already coded in. > > > If not than maybe some functions like the following would be useful. > > bool CheckSelection(char* selection) > int CheckVarexp(char* varexp) > // return 0 if wrong > // return 1 if 1 dim histogram is drawn > // return 2 if 2 dim histogram is drawn > // return 3 if 3 dim histogram is drawn > + some other variables depnding on wheter it is going to be draw to > predefined histogram Draw("Energy>>histo") or to event list etc. > > Miro Helbich >
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