imap: Apply a function to each element of a vector, and its index
Description
imap(x, ...), an indexed map, is short hand for
map2(x, names(x), ...) if x has names, or map2(x, seq_along(x), ...)
if it does not. This is useful if you need to compute on both the value
and the position of an element.
Usage
imap(.x, .f, ...)
imap_lgl(.x, .f, ...)
imap_chr(.x, .f, ...)
imap_int(.x, .f, ...)
imap_dbl(.x, .f, ...)
imap_vec(.x, .f, ...)
iwalk(.x, .f, ...)
Value
A vector the same length as .x.
Arguments
.x
A list or atomic vector.
.f
A function, specified in one of the following ways:
A named function, e.g. paste.
An anonymous function, e.g. \(x, idx) x + idx or
function(x, idx) x + idx.
A formula, e.g. ~ .x + .y. You must use .x to refer to the
current element and .y to refer to the current index.
No longer recommended.
Wrap a function with in_parallel() to declare that it should be performed
in parallel. See in_parallel() for more details.
Use of ... is not permitted in this context.
...
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 |> map(f, 1, 2, collapse = ",")
# do:
x |> 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.
See Also
Other map variants:
lmap(),
map(),
map2(),
map_depth(),
map_if(),
modify(),
pmap()