safely {purrr} | R Documentation |
These functions wrap functions so that instead of generating side effects through printed output, messages, warnings, and errors, they return enhanced output. They are all adverbs because they modify the action of a verb (a function).
safely(.f, otherwise = NULL, quiet = TRUE) quietly(.f) possibly(.f, otherwise, quiet = TRUE) auto_browse(.f)
.f |
A function, formula, or atomic vector. If a function, it is used as is. If a formula, e.g.
This syntax allows you to create very compact anonymous functions. If character vector, numeric vector, or list, it
is converted to an extractor function. Character vectors index by name
and numeric vectors index by position; use a list to index by position
and name at different levels. Within a list, wrap strings in |
otherwise |
Default value to use when an error occurs. |
quiet |
Hide errors ( |
safely
: wrapped function instead returns a list with
components result
and error
. One value is always NULL
.
quietly
: wrapped function instead returns a list with components
result
, output
, messages
and warnings
.
possibly
: wrapped function uses a default value (otherwise
)
whenever an error occurs.
safe_log <- safely(log) safe_log(10) safe_log("a") list("a", 10, 100) %>% map(safe_log) %>% transpose() # This is a bit easier to work with if you supply a default value # of the same type and use the simplify argument to transpose(): safe_log <- safely(log, otherwise = NA_real_) list("a", 10, 100) %>% map(safe_log) %>% transpose() %>% simplify_all() # To replace errors with a default value, use possibly(). list("a", 10, 100) %>% map_dbl(possibly(log, NA_real_)) # For interactive usage, auto_browse() is useful because it automatically # starts a browser() in the right place. f <- function(x) { y <- 20 if (x > 5) { stop("!") } else { x } } if (interactive()) { map(1:6, auto_browse(f)) } # It doesn't make sense to use auto_browse with primitive functions, # because they are implemented in C so there's no useful environment # for you to interact with.