Environment Browser

Description

Interrupt the execution of an expression and allow the inspection of the environment where browser was called from.

Usage

browser()

Details

A call to browser can be included in the body of a function. When reached, this causes a pause in the execution of the current expression and allows access to the R interpreter.

At the browser prompt the user can enter commands or R expressions. The commands are

c

(or just return) exit the browser and continue execution at the next statement.

cont

synonym for c.

n

enter the step-through debugger. This changes the meaning of c: see the documentation for debug.

where

print a stack trace of all active function calls.

Q

exit the browser and the current evaluation and return to the top-level prompt.

(Leading and trailing whitespace is ignored, except for return).

Anything else entered at the browser prompt is interpreted as an R expression to be evaluated in the calling environment: in particular typing an object name will cause the object to be printed, and ls() lists the objects in the calling frame. (If you want to look at an object with a name such as n, print it explicitly.)

The number of lines printed for the deparsed call can be limited by setting options(deparse.max.lines).

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

Chambers, J. M. (1998) Programming with Data. A Guide to the S Language. Springer.

See Also

debug, and traceback for the stack on error.