Debugging

Theory

• message just a generic notification as message

• warning something could go wrong

• error fatal error that stops execution

• condition generic concept indicating something unexpected happened

Functions

• traceback prints out the function call stack trace

• debug flags function for debug mode

• browser suspends execution and starts function in debug

• trace allows insert debugging code into a function

• recover allows to modify error behavior so function stact trace can be browsed

Examples

traceback

> mean(x)
Error in mean(x) : object 'x' not found
> traceback()
1: mean(x)

debug

> debug(lm)
> lm (y- x)
debugging in: lm(y - x)

And you continue to debugging window.

recover

> options(error=recover)
> read.csv("donotexitfile")
Error in file(file, "rt") : cannot open the connection
In addition: Warning message:
In file(file, "rt") :
  cannot open file 'donotexitfile': No such file or directory

Enter a frame number, or 0 to exit

1: read.csv("donotexitfile")
2: read.table(file = file, header = header, sep = sep, quote = quote, dec = dec, fill = fill, comment.char = comment.char, ...)
3: file(file, "rt")