Simultaneous Fit of Binned and Unbinned dataset

Roofit and RooStats
3

Hello Renato,

Adding log-likelihoods looks OK to me.

If you only want to construct a single log-likelihood, another option would be to construct a simultaneous PDF of the two pdfs, and make a combined dataset of the binned and unbinned data.
You can do this by making both datasets unbinned, and combining them as follows:

   RooCategory samples("samples", "samples");
   [... add category names here ...]

   RooArgSet datasetVars(x, y, weight, sample);
   std::map<std::string, RooDataSet*> sampleMap;
   sampleMap["xSampleName"] = &dataX;
   sampleMap["ySampleName"] = &dataY;
   
   RooDataSet combData("combData", "combined data", datasetVars, Index(sample), WeightVar(weight), Import(sampleMap));

Check out this constructor to see how you combine datasets from different categories:
https://root.cern.ch/doc/master/classRooDataSet.html#aeea71f616bd2cc6743f6869d31a4dbd5

To make the dataset unbinned, use the bin center of the histogram as x value and set the weight of the event to the bin content. You will get the exact same probabilities, but the “shape” of the dataset looks different.

A similar approach is being discussed in

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