safely: Wrap a function to capture errors

In purrr: Functional Programming Tools

Wrap a function to capture errors

Description

Creates a modified version of .f that always succeeds. It returns a list with components result and error. If the function succeeds, result contains the returned value and error is NULL. If an error occurred, error is an error object and result is either NULL or otherwise.

Usage

safely(.f, otherwise = NULL, quiet = TRUE)

Arguments

.f	A function to modify, specified in one of the following ways: A named function, e.g. mean. An anonymous function, e.g. ⁠\(x) x + 1⁠ or function(x) x + 1. A formula, e.g. ~ .x + 1. Only recommended if you require backward compatibility with older versions of R.
otherwise	Default value to use when an error occurs.
quiet	Hide errors (TRUE, the default), or display them as they occur?

Value

A function that takes the same arguments as .f, but returns a different value, as described above.

Adverbs

This function is called an adverb because it modifies the effect of a function (a verb). If you'd like to include a function created an adverb in a package, be sure to read faq-adverbs-export.

See Also

Other adverbs: auto_browse(), compose(), insistently(), negate(), partial(), possibly(), quietly(), slowly()

Examples

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()

purrr documentation built on Aug. 8, 2025, 7:38 p.m.