recover {utils} | R Documentation |
This function allows the user to browse directly on any of the
currently active function calls, and is suitable as an error option.
The expression options(error=recover)
will make this
the error option.
recover()
When called, recover
prints the list of current calls, and
prompts the user to select one of them. The standard R
browser
is then invoked from the corresponding
environment; the user can type ordinary S language expressions to be
evaluated in that environment.
When finished browsing in this call, type c
to return to
recover
from the browser. Type another frame number to browse
some more, or type 0
to exit recover
.
The use of recover
largely supersedes dump.frames
as an error option, unless you really want to wait to look at the
error. If recover
is called in non-interactive mode, it
behaves like dump.frames
. For computations involving large
amounts of data, recover
has the advantage that it does not
need to copy out all the environments in order to browse in them. If
you do decide to quit interactive debugging, call
dump.frames
directly while browsing in any frame (see
the examples).
WARNING: The special Q
command to go directly from the
browser to the prompt level of the evaluator currently interacts with
recover
to effectively turn off the error option for the next
error (on subsequent errors, recover
will be called normally).
Nothing useful is returned. However, you can invoke
recover
directly from a function, rather than through the error
option shown in the examples. In this case, execution continues
after you type 0
to exit recover
.
The R recover
function can be used in the same way as the
S-Plus function of the same name; therefore, the error option shown is
a compatible way to specify the error action. However, the actual
functions are essentially unrelated and interact quite differently
with the user. The navigating commands up
and down
do
not exist in the R version; instead, exit the browser and select
another frame.
John M. Chambers (1998).
Programming with Data; Springer.
See the compatibility note above, however.
browser
for details about the interactive computations;
options
for setting the error option;
dump.frames
to save the current environments for later
debugging.
## Not run: options(error = recover) # setting the error option ### Example of interaction > myFit <- lm(y ~ x, data = xy, weights = w) Error in lm.wfit(x, y, w, offset = offset, ...) : missing or negative weights not allowed Enter a frame number, or 0 to exit 1:lm(y ~ x, data = xy, weights = w) 2:lm.wfit(x, y, w, offset = offset, ...) Selection: 2 Called from: eval(expr, envir, enclos) Browse[1]> objects() # all the objects in this frame [1] "method" "n" "ny" "offset" "tol" "w" [7] "x" "y" Browse[1]> w [1] -0.5013844 1.3112515 0.2939348 -0.8983705 -0.1538642 [6] -0.9772989 0.7888790 -0.1919154 -0.3026882 Browse[1]> dump.frames() # save for offline debugging Browse[1]> c # exit the browser Enter a frame number, or 0 to exit 1:lm(y ~ x, data = xy, weights = w) 2:lm.wfit(x, y, w, offset = offset, ...) Selection: 0 # exit recover > ## End(Not run)