# Create a new RStudio package project in a directory of your choice
# We'll assume it's called, "mypkg"
# Check "Create a git repository" if you use git!

# Packages we'll need
install.packages(c(
  "devtools",
  "usethis",
  "roxygen2",
  "testthat"
))


# In Tools > Project Options > Build Tools make sure both
# "Use devtools package functions if available", and
# "Generate documentation with Roxygen" are checked (accept defaults)

# Take a look at R/hello.R and man/hello.Rmd... then delete
tryCatch(
  file.remove(c("R/hello.R", "man/hello.Rd")),
  error = NULL
)

# Oops, you've just realised you do want to use git!
install.packages("git2r")
git2r::config()
usethis::use_git(message = "Initial commit")

# usethis is soooo useful
# Note: On my Windows installation this fails if the package is on a network drive
usethis::use_readme_md() # or, usethis::use_readme_rmd() for RMarkdown
usethis::use_mit_license("Your Name, Your Institution")
usethis::use_r("my-function")
usethis::use_testthat()
usethis::use_test("my-function")

# Go to my-function.R (or whatever you called it), and type or paste your
# code. Add any dependencies with:
#   devtools::use_package("pkgname")

# Then add some roxygen-compatible documentation to my-function.R
# Roxygen documentation lines start with #' and should appear before the code
# Don't forget "#' @import pkgname" for any dependencies and "#' @export"
tryCatch(file.remove("NAMESPACE"), error = NULL) # recreate with roxygen
devtools::document(roclets = c('rd', 'collate', 'namespace'))
# Shortcut for previous line: Ctrl + Shift + D

# Got to test-my-function.R (or whatever), and write some tests!
devtools::test()
# Shortcut for previous line: Ctrl + Shift + T

# Go to README.md (or README.Rmd if you went that way) and make some changes!

# Go to DESCRIPTION and make some changes!
# Enter the package Title: and Version:, and update the Description: field
# Add your name and email to the Author: and Maintainer: fields

# Check the package
devtools::check()
# Shortcut for previous line: Ctrl + Shift + E

# You're using git, right? Add and commit those changes
git2r::add(path = "*")
git2r::commit(message = "")

# Load your package
devtools::load_all(".")
# Shortcut for previous line: Ctrl + Shift + L

# Try out your function

# Why not install your own package?
devtools::install()
# Or, Build > Install and Restart, or shortcut: Ctrl + Shift + B

# Now to use it, just attach the library
library(mypkg)
# or, use the "pkgname::function()" syntax
# Either way, enjoy your new personal R package!