future_modify: Modify elements selectively via futures

In furrr: Apply Mapping Functions in Parallel using Futures

Modify elements selectively via futures

Description

These functions work the same as purrr::modify() functions, but allow you to modify in parallel.

Usage

future_modify(
  .x,
  .f,
  ...,
  .options = furrr_options(),
  .env_globals = parent.frame(),
  .progress = FALSE
)

future_modify_at(
  .x,
  .at,
  .f,
  ...,
  .options = furrr_options(),
  .env_globals = parent.frame(),
  .progress = FALSE
)

future_modify_if(
  .x,
  .p,
  .f,
  ...,
  .else = NULL,
  .options = furrr_options(),
  .env_globals = parent.frame(),
  .progress = FALSE
)

Arguments

.x	A vector.
.f	A function specified in the same way as the corresponding map function.
...	Additional arguments passed on to the mapped function. We now generally recommend against using ... to pass additional (constant) arguments to .f. Instead use a shorthand anonymous function: # Instead of x |> future_map(f, 1, 2, collapse = ",") # do: x |> future_map(\(x) f(x, 1, 2, collapse = ",")) This makes it easier to understand which arguments belong to which function and will tend to yield better error messages.
.options	The future specific options to use with the workers. This must be the result from a call to furrr_options().
.env_globals	The environment to look for globals required by .x and .... Globals required by .f are looked up in the function environment of .f.
.progress	A single logical. Should a progress bar be displayed? Only works with multisession, multicore, and multiprocess futures. Note that if a multicore/multisession future falls back to sequential, then a progress bar will not be displayed. Warning: The .progress argument will be deprecated and removed in a future version of furrr in favor of using the more robust progressr package.
.at	A logical, integer, or character vector giving the elements to select. Alternatively, a function that takes a vector of names, and returns a logical, integer, or character vector of elements to select. : if the tidyselect package is installed, you can use vars() and tidyselect helpers to select elements.
.p	A single predicate function, a formula describing such a predicate function, or a logical vector of the same length as .x. Alternatively, if the elements of .x are themselves lists of objects, a string indicating the name of a logical element in the inner lists. Only those elements where .p evaluates to TRUE will be modified.
.else	A function applied to elements of .x for which .p returns FALSE.

Details

From purrr:

Since the transformation can alter the structure of the input; it's your responsibility to ensure that the transformation produces a valid output. For example, if you're modifying a data frame, .f must preserve the length of the input.

Value

An object the same class as .x

Examples

plan(multisession, workers = 2)

# Convert each col to character, in parallel
future_modify(mtcars, as.character)

iris |>
 future_modify_if(is.factor, as.character) |>
 str()

mtcars |>
  future_modify_at(c(1, 4, 5), as.character) |>
  str()

furrr documentation built on March 31, 2026, 5:06 p.m.