When Things Don’t Work: Some Debugging Tips

class: center, middle, title-slide

.title[
# When Things Don’t Work: Some Debugging Tips
]
.author[
### Luke Tierney
]
.institute[
### University of Iowa
]
.date[
### 2025-01-17
]

---

Sometimes code you write doesn't work. That's OK, it happens to everyone.

Here are a few pointers on how to get things working.

* If you get an error message, read what the message says. Sometimes
  that is all it takes.

* Read the whole message: sometimes the most important part is at the
  beginning.

* If the message doesn't make sense to you, try Google: often someone
  else has asked about the same issue and received a useful answer.

* Simplify your code.

* Look carefully at intermediate results.
    * Replace complicated data by something smaller and simpler.
    * In the process you may find your mistake.

* Finding your bug usually involves double checking all the things you
  are sure you did right until you find the one you didn't.

---

If you can't resolve things yourself you may need to ask for help.

* When you ask for help, it is best to reduce your problem to a
  simple, reproducible example (`reprex`): The smallest set of
  expressions you can create that will show the problem starting with
  a fresh R session.

* In the process of creating a `reprex` you may figure out what is
  wrong.

* If you don't find your problem in putting together a `reprex`, you
  have something you can post on the **Q&A** discussion board that
  someone else can look at and try out.

* To make it easier to someone to try out your reprex, it is important
  to post it as text that someone can copy and paste into their R
  session, **not** as a screen shot.

Some References:

* [Reprex do’s and
  don’ts](https://reprex.tidyverse.org/articles/reprex-dos-and-donts.html)
  vignette in the
  [`reprex`](https://cran.r-project.org/package=reprex) package.
* [Common
  problems](https://r4ds.hadley.nz/data-visualize.html#common-problems)
  section in [R for Data Sceince](https://r4ds.hadley.nz/index.html).
* [Debugging](https://adv-r.hadley.nz/debugging.html) chapter in
  [Advanced R](https://adv-r.hadley.nz/index.html).

//adapted from Emi Tanaka's gist at //https://gist.github.com/emitanaka/eaa258bb8471c041797ff377704c8505