I want to build a roofit pdf which contains a step function. For example, g(x,a)*step(x,b) where a and b are the parameters of g and step functions, which need to be obtained by fitting. I have got the g(x,a) but I don’t know how to build step function in the roofit.

Hi @zebing_wang ! Have a look at the RooStepFunction , which takes a list of boundaries and coefficients to describe a general step function. You can turn such a step function into a PDF by using the RooWrapperPdf class. Then, you can multiply your PDFs with a RooProdPdf . In case it is simpler to ju…

Add step function in the final pdf

Roofit and RooStats

jonas July 20, 2022, 11:23am 5

Just for reference, this separate question was followed up on in a separate thread: