How can I obtain sWeights with zfit?

I have a fit to the signal region using zfit and fitting with an ExtendedUnbinnedNLL. My models are a signal and a background PDF.

How can I obtain the sWeights for background subtraction?

I had a look already at hepstats, they seem to provide many high-level tools. However, it was not clear to me how to use them.

Solution

The best way is to directly use the compute_sweights function provided by hepstats. Assuming you have your models signal and background, both fit extended to data, that would read as

from hepstats.splot import compute_sweights

sweights = compute_sweights(zfit.pdf.SumPDF([signal, background]), data)

bkg_sweights = sweights[Nbkg]
sig_sweights = sweights[Nsig]