Hello,
I understand that the only way to expand an existing TTree database is by adding additional. However, how would one add data to a TTree which is relevant to a specific data item of a TObjArray (on an existing branch) and maintain a data hiarchial organization?
An example: When dealing with particle tracking drift chambers, one begins with a set of drift times for each sense wire in a given particle track event. These drift times are stored in a drift structure which is listed in a TObjArray.
Data stored in first branch (called raw) during first pass of data:
class TRawData
{
Int_t run number,
Int_t fill number,
...
TClonesArray *wires; // wires("TMpxEvent")
}
with
class TMpxEvent
{
Int _t index;
Int_t time;
T3DPoint p1;
T3DPoint p2;
...
}
Once this database of particle track events is create, drift spectrums are created using the entire data set which map sense wire drift times to distances. Now, how would I incorporate this sense wire distance information into the TTree such that I can reference it relative to each of the sense wire drift structures?
Following first pass, I can do
tree->Draw("wires.time"); // works great.
Following the second pass over data, I would like to do the following:
tree->Draw("wires.distance","time = xxx && index = xxx");
I understand this can be accomplished by moving all the sense wire data (TMpxEvent) directly onto the branch and performing a tree->Fill() for each wire, but that would require run_number, fill_number... etc in TRawData be written up to 50 times more often than necessary in the TFile.
William J Deninger
This archive was generated by hypermail 2b29 : Tue Jan 04 2000 - 00:34:32 MET