22.8 Debug()

Another approach is to call a function that inserts the browser() call:

• debug() inserts a browser statement in the first line of the specified function. undebug() removes it. Alternatively, you can use debugonce() to browse only on the next run.

• utils::setBreakpoint() works similarly, but instead of taking a function name, it takes a file name and line number and finds the appropriate function for you.

These two functions are both special cases of trace(), which inserts arbitrary code at any position in an existing function. trace() is occasionally useful when you’re debugging code that you don’t have the source for. To remove tracing from a function, use untrace(). You can only perform one trace per function, but that one trace can call multiple functions.