RE: Using Parameters in TTreeFormula's?

Hi Robert,

How will you actually use this feature? Do you plan on minizing for each individual events or do minimize for all events?

Cheers,
Philippe

-----Original Message-----
From: owner-roottalk_at_pcroot.cern.ch [mailto:owner-roottalk_at_pcroot.cern.ch] On Behalf Of Robert Feuerbach
Sent: Wednesday, October 11, 2006 10:42 AM To: roottalk_at_pcroot.cern.ch
Subject: [ROOT] Using Parameters in TTreeFormula's?

Hi,

Are there plans to permit normal TFormula parameters in an expression using a TTreeFormula? For instance, I'd like to write something like:

TTreeFormula totEdiff("totEdiff",

                      "electronP-([0]*preshowerE+[1]*showerE)",tree);

where 'electronP', 'preshowerE' and 'showerE' are simple leafs in tree. This can be done in TFormula's, but does not appear to work in TTreeFormula's. In TTreeFormula::DefinedVariable fNpar is set to 0 and the class never looks back.

I'm trying to write a general routine to minimize expressions in terms of tree variables by varying the set of parameters, but the TTreeFormula's are completely unaware of the normal '[0]'-like parameters. I know it can by minimized by writing a macro using TFitter and TMinuit directly, but I'd like to have a more general implementation since this is common task. It could even evolve into a TTree::Minimize kind of method.

Thank you,
Rob Feuerbach

/***************************************************


 * Dr. Robert J. Feuerbach       feuerbac_at_jlab.org *

 * 12000 Jefferson Avenue       CEBAF Center  A120 *

 * Suite 4                  Office: (757) 269-7254 *

 * Newport News, VA 23606     Page:       584-7254 *

 * Fax: (757) 269-5703               Mailstop 12H3 *

 ***************************************************/