R imap -- purrr
imap_xxx(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.
purrr::imap is located in package purrr. Please install and load package purrr before use.
imap(.x, .f, ...)
imap_lgl(.x, .f, ...)
imap_chr(.x, .f, ...)
imap_int(.x, .f, ...)
imap_dbl(.x, .f, ...)
imap_raw(.x, .f, ...)
imap_dfr(.x, .f, ..., .id = NULL)
imap_dfc(.x, .f, ...)
iwalk(.x, .f, ...)
.x
A list or atomic vector.
.f
A function, formula, or vector (not necessarily atomic). If a
function, it is used as is. If a
formula, e.g.
~ .x + 2, it is converted to a function. There are three ways to refer to the arguments:
- For a single argument function, use .
- For a two argument function, use .x and .y
- For more arguments, use ..1, ..2, ..3 etc
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. If a component is not present, the value of
.default will be returned.
...
Additional arguments passed on to the mapped function.
.id
Either a string or NULL. If a string, the output will contain a variable with that name, storing either the name (if .x is named) or the index (if .x is unnamed) of the input. If NULL, the default, no variable will be created. Only applies to _dfr variant.
install.packages("purrr", repo="http://cran.r-project.org", dep=T)
library(purrr)
# is the value, and the second is the position
imap_chr(sample(10), ~ paste0(.y, ": ", .x))
iwalk(mtcars, ~ cat(.y, ": ", median(.x), "\n", sep = ""))
Return Values: A vector the same length as .x.
See Also: Other map variants: invoke(), lmap(), map2(), map_if(), map(), modify()
Same Names: iplots::imap
