The tutorials have a few examples. (I find those by grep -R createHistogram $ROOTSYS/tutorials/):
- ROOT: tutorials/roofit/rf301_composition.C File Reference
- ROOT: tutorials/roofit/rf302_utilfuncs.C File Reference
No, it samples the PDF, and writes that into a histogram. The fit curves you see when plotting also sample the PDF, but they might sample it at different points. That depends on the binning you pass.
That’s because it’s creating a histogram of the PDF, that is, it’s normalised to unity. If you want it scaled to data, you need an extended fit model, and use RooFit::Extended(), as mentioned in the documentation of the function:
https://root.cern.ch/doc/master/classRooAbsReal.html#a6659d2c301e5cd65b83ee8c9422c2553
Alternatively, you just create the normalised histogram and use hist->Scale(nData) to scale it to the amount of data.
Yes, almost. It saves only the curve that was plotted. It doesn’t remember where it came from. That means that the resolution of the curve (the point spacing, the range) depend on how wide the plot range was and how many bins it had etc. If you now decide that you need more points or a different range, you cannot do it, because the PDF information is not saved. If you are happy with what you see, though, you can use that.
I don’t know what you mean. I guess you would have to attach a picture.
If you decide to save curves, note that RooCurve derives from TGraph, so you can use all the functions from TGraph to read out points etc.