Understanding the useDynLib() Function in R Package Namespace Files

When building an R package that relies heavily on shared objects compiled by a Makefile, it’s essential to understand how to use the useDynLib() function correctly in the namespace file. This function plays a crucial role in linking the shared object to the package, but its usage can be tricky. In this article, we’ll delve into the details of useDynLib(), explore common pitfalls, and provide practical advice on how to get it right.

What is useDynLib()?

The useDynLib() function is used in R packages to specify the shared object library that should be linked during package installation. This function is typically used in the namespace file (R/NAMESPACE) of an R package.

Why is useDynLib() Important?

When an R package relies on a shared object compiled by a Makefile, it’s essential to ensure that this shared object is properly linked to the package during installation. The useDynLib() function facilitates this process by specifying the name of the shared object library that should be linked.

Common Issues with useDynLib()

When using useDynLib(), there are several common issues that developers may encounter, including:

• The shared object is not found during installation.
• The shared object has a different name than expected.
• The Makefile compilation process does not produce the correct shared object.

Understanding the Correct Usage of useDynLib()

To use useDynLib() correctly, it’s essential to understand that the first argument should be the name of the package, followed by the . and then the name of the shared object. For example:

useDynLib("myPackage")

This tells R that the shared object library named “myPackage” should be linked during installation.

Quotes in useDynLib()

The quotes around the package name are optional, but they’re recommended for clarity and to avoid potential issues with package names. For example:

useDynLib("myPackage")

or

useDynLib("My Package")

This tells R that the shared object library named “My Package” should be linked during installation.

Using useDynLib() with Makefile Compilation

When using a Makefile to compile C and Fortran code, it’s essential to ensure that the shared object is produced in the correct location. By default, the shared object will be produced in the project directory, but it may not be copied to the package installation directory.

To overcome this issue, you can use the R CMD build command with the -i option to specify the installation directory for the shared object.

For example:

R CMD build -i myPackage

This tells R to produce a debug version of the shared object in the package installation directory.

Best Practices for Using useDynLib()

Here are some best practices to keep in mind when using useDynLib():

• Use quotes around the package name to avoid potential issues with package names.
• Specify the correct file extension (.so or .dll) depending on your operating system.
• Ensure that the shared object is produced in the correct location by using the R CMD build command with the -i option.
• Use a Makefile to compile C and Fortran code, but consider dropping the compilation process altogether if it’s not necessary.

Conclusion

In conclusion, the useDynLib() function plays a crucial role in linking shared object libraries to R packages. By understanding its usage, developers can overcome common issues and ensure that their packages are properly linked during installation. By following best practices and using quotes around package names, developers can write efficient and reliable namespace files that work seamlessly with Makefile compilation.

Additional Resources

For more information on building R packages, including the use of useDynLib(), check out the official R documentation for Creating Packages and Linking to Shared Libraries.

Last modified on 2023-08-30