RooFit Product returns 0x0

From: Stephan Zimmer <zimmerst_at_googlemail.com>
Date: Sat, 11 Sep 2010 03:52:24 +0200

Hi Rooters,
after having worked with ROOT for quite some time, I now started exercising RooFit. It's quite impressive though in my opinion it lacks the clarity of the general ROOT program. Anyways, I'm trying to build up a Likelihood Ltot which is a product of 3 single Likelihood functions L1, L2, L3. suppose I have a model "model"
  RooDecay model("model","observed
spectrum",t,tau,gaussm,RooDecay::SingleSided) and then I create 3 datasets from this model

  // create some data for the histogram to be filled...   RooDataSet* data1 = model.generate(t,10000); // create a dataset from gauss-pd
f
  RooDataSet* data2 = model.generate(t,10000); // create a dataset from gauss-pd
f
  RooDataSet* data3 = model.generate(t,10000); // create a dataset from gauss-pd
f

Building the Negative-Log-Likelihood function for each of them works just fine

 RooAbsReal* nll1 = model.createNLL(*data1,NumCPU(2));
 RooAbsReal* nll2 = model.createNLL(*data2,NumCPU(2));
 RooAbsReal* nll3 = model.createNLL(*data3,NumCPU(2));

The RooArgSet is still a pointer referencing to some real memory address  RooArgSet *arg = new RooArgSet(*nll1,*nll2,*nll3); But the product then
 RooProduct *prod = new RooProduct("prod","product NLL",&arg) I get
 Error: Symbol null is not defined in current scope :0:

Can some of you guys who are more proficient with RooFit help me figure out how to fix this? Your help is greatly appreciated.

The general idea is to take N likelihood functions and multiply them for later subject to MINUIT minimization.
Cheers,
Stephan Received on Sat Sep 11 2010 - 03:52:30 CEST