See Methods in Disentangling sources of clock-like mutations in germline and soma, doi.org/10.1101/2023.09.07.556720
.
We assume that independent distributions govern the signature compositions of the age-dependent and age-independent mutations and denote them
Given linear dependence of the number of mutations on age,
and for Poisson regression with a log link function (not clock-like),
The code in inference.py
allows to find the two distributions,