PREVIOUSVALUE DAX Function
See the article here: https://www.linkedin.com/pulse/runge-kutta-limits-dax-greg-deckler-microsoft-mvp-
What we need is a function that will essentially allow recursion in specific circumstances in DAX and get around the circular reference issues. This would also make Kaplan-Meier calculations much easier as well. See this article:
https://www.linkedin.com/pulse/kaplan-meier-survival-curves-power-bi-greg-deckler-microsoft-mvp-