27 R Debugging: General

27.1 Debugging tool

Function	Explanation
`traceback()`	prints out the function call stack after an error occurs; does nothing if there is no error
`debug()`	flags a function for `debug` mode which allows to step through execution of a function one line at a time
`undebug()`	to take off the `debug` mode flags from a function
`debugonce()`	flags a function for `debug` mode only once; the function does not need `undebug` after it runs once.
`browser()`	suspends the execution of a function wherever it is called and puts the function in debug mode
`trace()`	allows you to insert debugging code into a function a specific places
`recover()`	allows to modify the error behavior so that you can browse the function call stack

In the Debug mode of browser window, you can move around the function:

Type n to execute the next line of code (RStudio: Press Enter or F10 or the relevant debug toolbar icon)
Type s to step into the current function call (RStudio: Press Shift+F4 or the relevant debug toolbar icon)
Type f to finish remaining of the current function or loop (RStudio: Press Shift+F7 or the relevant debug toolbar icon)
Type c to continue the execution until the next breakpoint is encountered (RStudio: Press Shift+F5 or the relevant debug toolbar icon)
Type Q to stop and exit the debug mode (RStudio: Press Shift+F8 or the relevant debug toolbar icon)
If you have a variable names as n, s, f, c, Q, then use print(variable_name)
You can also use other standard R commands to explore the objects in the function environment.