browser                 package:base                 R Documentation

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.

