Function reference • purrr

Map family

The map(.x, .f) functions transforms each element of the vector .x with the function .f, returning a vector defined by the suffix (_lgl, _chr() etc). walk() is a variant for functions called primarily for their side-effects; it returns .x invisibly.

As well as functions, .f, can take numbers and characters (used as a shorthand for [[), and formulas (used as a succint function definition). See details in as_mapper()

map() map_lgl() map_int() map_dbl() map_chr() map_vec() walk(): Apply a function to each element of a vector

as_mapper(): Convert an object into a mapper function

Map variants

A rich set of variants builds on the basic idea of map(): modify() modifies “in place”, returning a vector the same type as .x; map2() iterates over two vectors in parallel; pmap() (parallel map) iterates over a list of vectors; imap() (index map) is a shortcut for the common pattern map2(x, names(x)).

map_if() map_at(): Apply a function to each element of a vector conditionally

map_depth() modify_depth(): Map/modify elements at given depth

map2() map2_lgl() map2_int() map2_dbl() map2_chr() map2_vec() walk2(): Map over two inputs

pmap() pmap_lgl() pmap_int() pmap_dbl() pmap_chr() pmap_vec() pwalk(): Map over multiple input simultaneously (in "parallel")

modify() modify_if() modify_at() modify2() imodify(): Modify elements selectively

modify_tree(): Recursively modify a list

imap() imap_lgl() imap_chr() imap_int() imap_dbl() iwalk(): Apply a function to each element of a vector, and its index

lmap() lmap_if() lmap_at(): Apply a function to list-elements of a list

Predicate functionals

A predicate function is a function that either returns TRUE or FALSE. The predicate functionals take a vector and a predicate function and do something useful.

detect() detect_index(): Find the value or position of the first match

every() some() none(): Do every, some, or none of the elements of a list satisfy a predicate?

has_element(): Does a list contain an object?

head_while() tail_while(): Find head/tail that all satisfies a predicate.

keep() discard() compact(): Keep/discard elements based on their values

keep_at() discard_at(): Keep/discard elements based on their name/position

Plucking

Getting or setting a single element.

pluck() `pluck<-`() pluck_exists(): Safely get or set an element deep within a nested data structure

chuck(): Get an element deep within a nested data structure, failing if it doesn't exist

pluck_depth(): Compute the depth of a vector

modify_in() assign_in(): Modify a pluck location

attr_getter(): Create an attribute getter function

Other vector transforms

A grab bag of useful tools for manipulating vectors.

accumulate() accumulate2(): Accumulate intermediate results of a vector reduction

list_c() list_cbind() list_rbind(): Combine list elements into a single data structure

list_flatten(): Flatten a list

list_assign() list_modify() list_merge(): Modify a list

list_simplify(): Simplify a list to an atomic or S3 vector

list_transpose(): Transpose a list

reduce() reduce2(): Reduce a list to a single value by iteratively applying a binary function

Superseded

Superseded functions have been replaced by superior solutions, but due to their widespread use will not go away. However, they will not get any new features and will only receive critical bug fixes.

flatten() flatten_lgl() flatten_int() flatten_dbl() flatten_chr() flatten_dfr() flatten_dfc(): Flatten a list of lists into a simple vector

map_dfr() map_dfc() imap_dfr() imap_dfc() map2_dfr() map2_dfc() pmap_dfr() pmap_dfc(): Functions that return data frames

as_vector() simplify() simplify_all(): Coerce a list to a vector

transpose(): Transpose a list.

Adverbs

Adverbs modify the action of a function; they take a function as input and return a function with modified action as output.

auto_browse(): Wrap a function so it will automatically browse() on error

compose(): Compose multiple functions together to create a new function

insistently(): Transform a function to wait then retry after an error

negate(): Negate a predicate function so it selects what it previously rejected

partial(): Partially apply a function, filling in some arguments

possibly(): Wrap a function to return a value instead of an error

quietly(): Wrap a function to capture side-effects

safely(): Wrap a function to capture errors

slowly(): Wrap a function to wait between executions

Misc

array_branch() array_tree(): Coerce array to list

rate_delay() rate_backoff() is_rate(): Create delaying rate settings

progress_bars: Progress bars in purrr