::: {.callout-important title="Optional: not covered in the 2026 course"}
This document is **not** part of any taught session. Nobody is going to lecture it at you, nobody is going to grade you on it, and you can ignore it completely without falling behind.

It exists because it is a thing you will plausibly need next, and because it is easier to hand you something that works than to hand you a citation and wish you luck. Everything here runs end to end on the same machine setup you used in class. Every number and every figure on this page was produced by a chunk in this file: there are no screenshots of R output anywhere in the ancillary package.

**How to work through it alone.** Get the source (click the `</>` **Code** button at the top right, then **View Source**, and copy it into a `.qmd` file: or open the `.qmd` you were given directly), run the chunks in order, and read the prose between them: the prose is where the argument lives. Slow fits are identified in the prose, and precomputed fits load a shipped result while still showing you the code that produced it. Folded **Depth** boxes are optional extras; folded **Stuck?** boxes are hints. Open whichever you need and ignore the other. Exercises have a **Solution** tab: you are working alone, so use it.
:::
