---
title: "factor"
source: https://www.jemoka.com/posts/kbhfactor/
---

in probability, a factor \(\phi\) is a value you can assign to each distinct value in a discrete distribution which acts as the probability of that value occurring. They are considered parameters of the discrete distribution.
If you don&rsquo;t have discrete variables, factors allow you to state \(p(x|y)\) in terms of a function \(\phi(x,y)\).
See also Rejection Sampling
factor operations factor product \begin{equation} \phi_{3} (x,y,z) = \phi_{1} (x,y) \cdot \phi_{2}(y,z) \end{equation}
factor marginalization \begin{equation} \phi(x) = \sum_{y=Y} \phi(x,y) \end{equation}
factor conditioning Removing any rows not consistent with evidence. Say you know \(Y=1\), remove all rows that say \(Y=0\).
