How to use the command 'R' (with examples)

The R language interpreter is a powerful tool used for statistical computing and graphics. As an open-source language, it is widely utilized by statisticians, data scientists, and analysts for a myriad of data analysis tasks. The R command provides several functionalities through its various options and arguments, enabling users to execute R scripts, run expressions, check packages, and more. Below, we’ll explore different use cases of the ‘R’ command and illustrate how one can make the most out of this versatile interpreter.

Use case 1: Start a REPL (interactive shell)

Code:

R

Motivation:

Starting a REPL, or Read-Eval-Print Loop, allows users to interact with R in real-time. This is particularly useful for data analysis and exploratory tasks, where you might want to iteratively check results and make ongoing adjustments to your code on the fly. It provides an interactive environment where users can input expressions, see immediate results, and make rapid iterations, thereby enhancing productivity and comprehension.

Explanation:

• R: Invoking the R command without any options initializes the interactive shell or REPL. This mode is the default behavior of the R interpreter when no other arguments are provided.

Example Output:

Upon entering the R command, the shell opens with a startup message and displays the R prompt:

R version 4.1.3 (2021-03-10) -- "One Push-Up"
Copyright (C) 2021 The R Foundation for Statistical Computing
Platform: x86_64-apple-darwin17.0 (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

  Natural language support but running in an English locale

R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

>

Use case 2: Start R in vanilla mode

Code:

R --vanilla

Motivation:

Starting R in vanilla mode is beneficial when you want a clean session, free of saved workspaces, site profiles, or other preloaded configurations. This is particularly advantageous in scripts or analyses where reproducibility is crucial and you want to ensure that no extraneous variables or settings from previous sessions affect your environment.

Explanation:

• R: Calls the R interpreter.
• --vanilla: This option launches R without loading any startup files (such as .Rdata and initialization scripts) and does not save the workspace at the session’s end. Essentially, it ensures a blank slate for the session.

Example Output:

The output resembles the standard REPL startup but without loading any workspace from a previous session:

R version 4.1.3 (2021-03-10) -- "One Push-Up"
...
Type 'q()' to quit R.

>

Use case 3: Execute a file

Code:

R -f path/to/file.R

Motivation:

Executing an R script file directly from the command line can automate analyses, especially in a production environment or in predefined workflows. This capability allows for batch processing of data and can be integrated into larger automated systems such as data pipelines or cron jobs, facilitating seamless and efficient processing.

Explanation:

• R: Initiates the R interpreter.
• -f: This option specifies that the following argument is the path to an R script file that should be executed.
• path/to/file.R: This is the file path to the R script that will be executed. The script contains R code which will be run in sequence.

Example Output:

Running a script might produce an output like:

[1] "Data processing complete."
Summary Statistics:
  Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
-3.0000 -1.1200  0.1600  0.2203  1.3900  2.8400 

Use case 4: Execute an R expression and then exit

Code:

R -e expr

Motivation:

Using the R interpreter to evaluate a quick expression directly from the command line can be extremely efficient for rapid tasks without requiring the overhead of starting a full R session. This can be useful for quick calculations, small data analyses, or testing snippets of code without leaving the terminal environment.

Explanation:

• R: Starts the R interpreter.
• -e: This option indicates that the following is an R expression (e.g., R -e 'sqrt(16)') to be evaluated by the R interpreter.
• expr: This represents the R expression to be executed.

Example Output:

Executing R -e 'print(sqrt(16))' may result in:

[1] 4

Use case 5: Run R with a debugger

Code:

R -d debugger

Motivation:

Running R with a debugger is an invaluable practice when you need to identify and fix bug-ridden scripts. This allows for step-by-step execution of R code, inspection of variable states, and assessment of function calls and their effects. Debugging is a critical part of developing robust code, particularly for complex data analyses or programming in R.

Explanation:

• R: The R interpreter is invoked.
• -d: This option indicates that R should run with a specified debugger.
• debugger: Specifies the debugger program to be used. For instance, gdb.

Example Output:

Starting R with a debugger like gdb might show:

GNU gdb (GDB) 8.1.1
...
(gdb) run
Starting program: /usr/bin/R 
...
(gdb)

Use case 6: Check R packages from package sources

Code:

R CMD check path/to/package_source

Motivation:

Checking an R package from source is crucial for developers to ensure that their package is CRAN-ready. This process verifies that the package meets R’s standards regarding documentation, code quality, and installation. The R CMD check command catches errors, warnings, and notes, providing indispensable feedback before submitting the package to a repository.

Explanation:

• R: The command begins by calling the R interpreter.
• CMD: Specifies that a command rather than an interactive session, will be executed.
• check: Directs R to verify the contents of the specified package source in terms of guidelines and standards.
• path/to/package_source: Path to the directory containing the package source files.

Example Output:

Running this command might yield:

* using R version 4.1.3 (2021-03-10)
* using platform: x86_64-pc-linux-gnu (64-bit)
* checking for file ‘path/to/package_source/DESCRIPTION’ ... OK
* checking package namespace information ... OK
* checking package dependencies ... OK
* checking if this is a source package ... OK
...

Use case 7: Display version

Code:

R --version

Motivation:

Displaying the version of R installed on your system is beneficial when ensuring compatibility with scripts, packages, or other users’ systems. Understanding which version of R you are utilizing helps in debugging, ensuring consistent project environments, and communicating with collaborators effectively.

Explanation:

• R: Calls the R executable.
• --version: Shows the installed version of R along with relevant platform information.

Example Output:

Executing this command typically results in output like:

R version 4.1.3 (2021-03-10) -- "One Push-Up"
Copyright (C) 2021 The R Foundation for Statistical Computing
Platform: x86_64-apple-darwin17.0 (64-bit)

Conclusion:

The R command is a diverse and valuable tool for anyone working within data science or statistical computing. By leveraging the aforementioned use cases, users can efficiently manage their workflows, enhance their productivity, and maintain consistent environments suitable for professional data analysis and development tasks. Each use case outlined provides a specific benefit that enhances the capability and functionality of working with R.