In csgillespie/efficient: Becoming an Efficient R Programmer

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Welcome to the Efficient R Programming answers sheet. Here you will find answers to the numerous exercises provided in the book Efficient R Programming.

Chapter 2

R Version

What version of R are you using? Is it the most up-to-date?

Your R version is stored in a variable called R.version. Enter these commands to find out the version.

r R.version R.version.string

This can be compared with the latest version, which is described on R's website: cran.r-project.org/. If you've not got the latest version, consider installing the latest version!
Do any of your packages need updating?

To find out which (if any) of your packages need updating use the following command:

r old.packages()

R Startup

What are the three locations where the startup files are stored? Where are these locations on your computer?

The three locations where startup files can be stored and used are R_HOME, HOME and the project's working directory. The specific locations of these places will vary from one computer to another but can be found using the following commands:

r R.home() path.expand("~") getwd()

See ?Startup for more details
For each location, does a .Rprofile or .Renviron file exist?

Navigate to the locations outlined above to find out.
Create a .Rprofile file in your current working directory that prints the message Happy efficient R programming each time you start R at this location.

To test if this works, restart the session (e.g. via Shift+Ctrl+F10 in RStudio) and see if the message appears. Creating the following line in a file called .Rprofile in your project's root directory will do this:

r message("Happy efficient R programming")
What happens to the startup files in R_HOME if you create them in HOME or local project directories?

The R_HOME startup files will be ignored. Likewise the HOME startup files will be ignored if there are local startup files.

RStudio

The first set of six exercises is about exploring and trying out RStudio interactively. There is no right answer in this case - the best approach is to play around.

Try modifying the look and appearance of your RStudio setup.

Again, there is no right answer to this question. It's worth experimenting a little until the setup is right for you. But it's not worth spending all day doing that from an efficiency perspective!
What is the keyboard shortcut to show the other shortcut? (Hint: it begins with Alt+Shift on Linux and Windows.)

On Linux and Windows machines Alt+Shift+K will show commonly used shortcuts.
Try as many of the shortcuts revealed by the previous step as you like. Write down the ones that you think will save you time, perhaps on a post-it note to go on your computer.

Again this is highly subjective and only a few handy examples are mentioned here. Ctl+Up can be particularly useful for navigating previous commands that have been partially entered. Ctl+D deletes the current line while Alt+Shift+Down copies it down.