def-user.qmd

# User settable defaults {#sec-def-user}

```{r}
#| include = FALSE
source("common.R")
```

## What's the pattern?

It's sometimes useful to give the user control over default values, so that they can set once per session or once for every session in their `.Rprofile`.
To do so, use `getOption()` in the default value.

Note that this pattern should general only be used to control the side-effects of a function, not its compute value.
The two primary uses are for controlling the appearance of output, particularly in `print()` methods, and for setting default values in generated templates.

Related patterns:

-   If a global option affects the results of the computation (not just its side-effects), you have an example of @sec-inputs-explicit.

## What are some examples?

## Why is it important?

## What are the exceptions?

## How do I use it?