Advanced Package Development | R Packages

Introduction

R packages are a powerful way to share your code and data with other users. Advanced package development involves creating robust, efficient, and well-documented packages that can be easily used and maintained. This tutorial will guide you through the advanced aspects of R package development, including structuring your package, using namespaces, and integrating tests and documentation.

Package Structure

A typical R package consists of several important components. The basic structure includes the following directories and files:

DESCRIPTION: Contains metadata about the package.
NAMESPACE: Defines which functions are exported and which are kept internal.
R/: Contains R scripts with the package's functions.
man/: Contains documentation files for the package functions.
tests/: Holds test files for package functions.

You can create a package structure using the devtools package:

R devtools::create("MyPackage")

This command creates a folder named MyPackage with the basic structure.

Using Namespaces

The NAMESPACE file is crucial for managing what functions are accessible to users and what functions are internal. Here’s how to create and manage this file:

Example NAMESPACE file:


                    export(my_function) 

                    import(ggplot2)

Use export() to specify which functions will be available to users of your package, and import() to bring in functions from other packages.

Documentation with roxygen2

Good documentation is essential. The roxygen2 package allows you to write documentation inline with your code. To use roxygen2, add comments directly above your functions:

Example function documentation:


                    #' My function title 

                    #' 

                    #' Description of the function. 

                    #' @param x Description of parameter x 

                    #' @return Description of return value 

                    #' @export 

                    my_function <- function(x) { 

                         return(x^2) 

                    }

After writing your documentation, run devtools::document() to generate the man/ files.

Testing Your Package

Writing tests is crucial for maintaining the quality of your package. The testthat package is commonly used in R for testing. Create a tests/testthat/ directory and add test files there. Here’s an example of a simple test:

Example test file:


                    library(testthat) 

                    context("My Function Tests") 

                    test_that("my_function works correctly", { 

                         expect_equal(my_function(2), 4) 

                         expect_error(my_function("a")) 

                    })

Run your tests using devtools::test() to ensure everything is functioning as expected.

Building and Checking Your Package

Once your package is complete with documentation and tests, you can build and check it. Use the following commands:

R devtools::build() devtools::check()

The build() function creates a tarball of your package, while check() runs a series of checks to ensure your package meets CRAN standards.

Conclusion

Advanced R package development involves creating a well-structured, documented, and tested package. By following the guidelines in this tutorial, you will be able to develop robust R packages that can be shared with the community. Remember to leverage tools like devtools, roxygen2, and testthat to enhance your development process.

Advanced Package Development in R