with your notations
Track* t = fEvent->GetTracks()->At(i);
gives you pointer to i-th track stored in TClonesArray.
See TClonesArray.h if you need more details.
Regards, Pasha.
--------------------------------------------------------------------------------
Dirk Meier writes:
>
>
> Hi
>
> I went to the famous eventa.cxx example and try to extract
> the data from the TClonesArray of Track.
>
> Therefore I modified eventa.cxx to
>
> //*CMZ : 1.00/09 24/04/97 11.01.18 by Rene Brun
> //*-- Author : Rene Brun 10/01/97
> {
> // This macro read all events generated by the test program Event
> // provided in $ROOTSYS/test.
> //
> // NOTE: Before executing this macro, you must have executed the macro
> eventload.
> //
> // This small program simply counts the number of bytes read and dump
> // the first 3 events.
>
> gROOT->Reset();
>
> // Connect file generated in $ROOTSYS/test
> TFile f("Event.root");
>
> // Read Tree named "T" in memory. Tree pointer is assigned the same name
> TTree *T = (TTree*)f.Get("T");
>
> // Create a timer object to benchmark this loop
> TStopwatch timer;
> timer.Start();
>
> // Start main loop on all events
> Event *event = new Event();
>
> TClonesArray *tracks = event->GetTracks();
>
> //TBranch *branch = T->GetBranch("event");
> //branch->SetAddress(&event);
>
> T->SetBranchAddress("event", &event);
> Int_t nevent = T->GetEntries();
> Int_t nb = 0;
> Float_t ran; // <--- declare a variable for some track value
> for (Int_t i=0;i<nevent;i++) {
> if(i%50 == 0) {
> printf("Event:%d ",i);
> ran = tracks.GetRandom(); // <-- !!!! here I do not know how to
> //retrieve data from TClonesArray!!!!!!!!!
> printf("has %d tracks at T=%f with value %f\n",
> event->fNtrack, event->fTemperature, ran);
> // retrieving event data like e.g. fNtrack or fTemperature works
> // how is it possible to access the data in the TClonesArray????
> }
> nb += T->GetEvent(i); //read complete event in
> memory
> if (i < 3) event->Dump(); //dump the first 3 events
> event->Clear(); //clear tracks array
> }
>
> // Stop timer and print results
> timer.Stop();
> Float_t mbytes = 0.000001*nb;
> Double_t rtime = timer.RealTime();
> Double_t ctime = timer.CpuTime();
> printf("RealTime=%f seconds, CpuTime=%f seconds\n",rtime,ctime);
> printf("You read %f Mbytes/Realtime seconds\n",mbytes/rtime);
> printf("You read %f Mbytes/Cputime seconds\n",mbytes/ctime);
> printf("%d events and %d bytes read.\n",nevent,nb);
>
> f.Close();
> }
>
> Could you give me an example of how to retrieve the data from the
> TClonesArray (this would likely solve the question I had in the
> last mail).
>
> merci bien
> Dirk
>