I am trying to make use of a composite pdf, similar to the RooFit example 201.
I have currently a working fit with three pdfs [pdf1, pdf2, pdf3] existing as RooHistFunc. I then build my model with
model = ROOT.RooRealSumPdf(“model”, “1+2+3”, [pdf1, pdf2, pdf3], [coeff1, coeff2]), where [coeff1, coeff2] exist as RooRealVar.
This works okay, but I would like to fix the contribution of pdf3 to be 5% of the total pdf. If I add a third constant coefficient, coeff3, to the set in the model definition, my fit no longer converges to coeff1+coeff2+coeff3 = 1. Could someone please help me to employ this behavior, as I cannot seem to find this type of procedure in a RooFit example.