04-functions.Rmd

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

# Functions {#functions}

You’ll need to organize your code into functions in order to use the code in a package.

Function structure:

```{r}
foo <- function(x) {
  x^2
}
```

You can call the function

```{r}
foo(5)
```

## Exercise

__Write your own function__

* Write a function
* Run it!
* Any problems? report back


## Functions in a package

In a real R package you DO NOT want to export all functions in the package. 

RStudio/`devtools`/`usethis`/etc. do put 

`exportPattern("^[^\\.]")`

in your `NAMESPACE` file by default. 

Important: Make sure to remove this and explicitly export functions that you want 
users to use with RStudio buttons or `devtools::document()` or similar.