Error when using ProfileLikelihoodCalculator GetInterval

Roofit and RooStats
1

Dear all,

I am trying to calculate an upper limit using the ProfleLikelihoodCalculator class. Although fitting works quite fine, I get the error message ‘Error - invalid parameter signal_yield specified for finding the interval limits’. The only solution I could find suggested to explicitly set the parameter non-const, but that didn’t help either. Moreover, I get the exact same error message when I set a different parameter to be the parameter of interest.

Here is what I am doing:
RooArgSet paramOfInterest(m_sigYield);
RooStats::ModelConfig modelConfig(“modelConfig”, new RooWorkSpace());
modelConfig.SetPdf(m_combinedModel);
modelConfig.SetParametersOfInterest(paramOfInterest);
RooRealVar myPOI = (RooRealVar) modelConfig.GetParametersOfInterest()->first();
myPOI->setConstant(false);
RooStats::ProfileLikelihoodCalculator pl_calculator(data, modelConfig);
pl_calculator.SetTestSize(0.05);
RooStats::LikelihoodInterval pl_interval = pl_calculator.GetInterval();

Here, data is a RooDataSet, m_combinedModel is a RooAddPdf and m_sigYield a RooRealVar.

I am very thankful for any response.

regards,
Johannes

2

Hi,
This should not happen. It means that the given parameter is not a variable of profiled likelihood function.
So, there is probably something fuzzy in the model. Could you please attach your workspace, including the dataset and ModelConfig object, so I could reproduce this problem

Best Regards

Lorenzo

3

Hi Lorenzo,

thank you very much for your quick answer. The workspace is attached.

regards,
Johannes
error_workspace.root (13.4 KB)

4

Hi,

It seems I am not getting this error in your model. I am doing:

root[] .x $ROOTSYS/tutorials/roostats/StandardProfileLikelihoodDemo("error_workspace.root","wspace","modelConfig","wu")

I have other errors when making the plot of the internal due to invalid fits, but this is another problem

Best Regards

Lorenzo

5

Hi Lorenzo,

thank you very much. The error disappears if I do not use my pdf directly but if I put it in a workspace first and retrieve it later when I’m calculating the limit as it happens when you read the workspace from a file. Your answer was a big help for me.

kind regards,
Johannes