How to Access Data via Cafe

by Pedro Mercadante - Last update on 15-Dec-2005

How To Make a Processor and Access the Data via Cafe

On d0server copy the following files to your work directory:







./ inv_mass InvMass

The first argument is the package name and the second is the processor name. The creates all the necessary .cpp, .hpp and linkdef.h. We should edit the inv_mass/src/InvMass.cpp. Basically in InvMass::begin() we initialize the histograms; in InvMass::processEvent(cafe::Event& event) we process events, do whatever we need and fill the histograms; and in InvMass::finish() we write the histograms.

To access the data we should look at
under the class list. We can click on cafe::Event and see all the objects. For exemple getEMscone is a Collection . To access it we need to define a object that is a collection and access the collection via a pointer:

Collection fro(event.getEMscone());

for(Collection::const_iterator it = fro.begin() ;

it = fro.end(); ++it)

Now we can access all objects defined in the class TMBEMCluster. For example, Px, Py, Pz:

float ele_pt = it->Pt() ;

float ele_px = it->Px() ;

float ele_py = it->Py() ;

float ele_pz = it->Pz() ;

float ele_E = it->E() ;

One note for the histograms: we define the histograms in the InvMass::begin() function and fill in the bool InvMass::processEvent(cafe::Event& event) function. So don't forget to declare the global variables in the .hpp file.

Topic revision: r2 - 2006-09-18 - SergioLietti

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