If you’d never previously written an R package, then you’ve probably never used R CMD check. But this is an essential tool for R package developers, and you are now an R package developer. (That is, if you’ve been doing your homework.)

R CMD check runs all sorts of checks on the contents of an R package, and gives warnings and error messages when it finds things that aren’t right. It also will run the examples in the .Rd files for each of your functions, as well as other automated tests that you’ve included. If a function uses a variable that doesn’t exist (due to a typo or a copy-paste error), R CMD check will often find it.

Before you submit a package to the Comprehensive R Archive Network (CRAN), you should first run R CMD check (including with the option --as-cran) and revise your package so that there are no warnings or errors.

From the command line

To run R CMD check from the command line, I will typically first build the package file (say brocolors_0.1.tar.gz) with R CMD build, and then I’ll type:

R CMD check brocolors_0.1.tar.gz

The output is quite verbose, but any warnings or errors will be quite prominent. Look through each of them carefully, and modify your package to resolve the problems.

For reasons that I don’t entirely understand, there’s a --as-cran flag that will do a few additional checks. If you’re considering submitting your package to CRAN, you should try it that way, too.

R CMD check --as-cran brocolors_0.1.tar.gz

With devtools

You can also run these checks from within R, using the devtools package.

Start R within your package directory, load the devtools library with library(devtools) and then type check(), just as you had used build() and install() to build and install the package.

Homework

Use R CMD check and R CMD check --as-cran or, with devtools, check().

Modify your package so that there are no errors or warnings.

You are now done with the essentials and have a proper R package!

Go back to the main page, or go to the page about putting your R package on GitHub.