06-dependencies.Rmd

```{r echo = FALSE}
knitr::opts_chunk$set(
  comment = "#>",
  warning = FALSE,
  message = FALSE
)
```


# Dependencies {#dependencies}

Dependencies = other R packages. 

There are (mostly) three types:

* Depends
* Imports
* Suggests

`Enhances` is used rarely

## Adding dependencies

- Add an entry in the `DESCRIPTION` file
- Add a declaration of what you are importing from the package:
    + all of the package, or (`@import package`)
    + certain functions (`@importFrom package function`)
    + there's no standard for where to do this. 
        + i like to do in a package named manual file (e.g., `foobar-package.R`) so you can keep track of all imports in one place
        + but some like to list imports in each file/function where they are used

You can do this manually or via `usethis::use_package('package_name')`

## Add a dependency to a package

### Exercise

Choose a package that's easy for you to work with. 

Add it to your package

Reinstall and load your package

Does it work?

## BONUS: What are system dependencies?