Chapter 6 Coding in a package

6.1 Edit code, run, modify, repeat

When developing a package, find whatever method is most efficient for you to develop the package quickly.

You want to be able to edit code, then run/test it, modify, rerun, modify, etc. until you are happy with it.

For some this may mean working in an IDE (RStudio) - for others this means a text editor and console - for others maybe Vim or Emacs.

Get used to the keyboard shortcuts or buttons to make this flow easy and quick.

devtools::load_all() (or equivalent buttons/shortcuts in IDE) is your friend - though beware you still want to check your package outside of a load all context (See 9)

6.2 Code

6.2.1 Exercise

Write your own function

• Write a function
• Put it in a file in your R package

6.3 Docs

Time to document your function!

Above your function start each line with #'. There’s many, many options for documenting functions.

6.3.1 Exercise

Let’s do a minimal set:

• Title
• Export tag
• Parameter definitions
• Return tag
• Examples

#' Multiply a number by 2
#' 
#' @export
#' @param x a numeric value. required
#' @return a number
#' @examples
#' multiply2(x = 5)
multiply2 <- function(x) {
  stopifnot(is.numeric(x))
  x * 2
}

6.4 Generate documentation

In RStudio push the document button or keyboard shortcut, or on the command line run devtools::document() or similar.

Notice what state your NAMESPACE file is in before and after.

6.5 Install the package

Now install the package.

• in RStudio: Install and Restart
• command line: devtools::install()
• restart your R session
• load your package library(packagename)
• Can you run your function?
  • if not, let’s dig in and sort it out

6.6 Yay!