I'm confused about the circular reference thing. Like, was there a reason to do the linear regression that way? Is there a secret story in a story where next week, in a spinoff / sequel episode, the data scientist responsible will explain why they took the weird/surprising choices they did?
It's a common excel trick in finance. For example, let say you have $0. If you borrow $1,000,000 at 5% interest, by end of year you'll be short $50k. That means you actually needed to borrow $1,050,000. But the extra $50K causes more interest ($2,500)... so you needed to borrow $1,052,500, which causes more interest... and so on.
Instead of doing some Excel Goal Seek or Solver or VBA macro, it's nice to let the excel "reactivity" handle it for you.
