map2 {purrr} | R Documentation |
These functions are variants of map()
iterate over multiple
arguments in parallel. map2()
and walk2()
are specialised for the two
argument case; pmap()
and pwalk()
allow you to provide any number of
arguments in a list.
map2(.x, .y, .f, ...) map2_lgl(.x, .y, .f, ...) map2_int(.x, .y, .f, ...) map2_dbl(.x, .y, .f, ...) map2_chr(.x, .y, .f, ...) map2_dfr(.x, .y, .f, ..., .id = NULL) map2_dfc(.x, .y, .f, ...) walk2(.x, .y, .f, ...) pmap(.l, .f, ...) pmap_lgl(.l, .f, ...) pmap_int(.l, .f, ...) pmap_dbl(.l, .f, ...) pmap_chr(.l, .f, ...) pmap_dfr(.l, .f, ..., .id = NULL) pmap_dfc(.l, .f, ...) pwalk(.l, .f, ...)
.x, .y |
Vectors of the same length. A vector of length 1 will be recycled. |
.f |
A function, formula, or atomic vector. If a function, it is used as is. If a formula, e.g.
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. Within a list, wrap strings in |
... |
Additional arguments passed on to |
.id |
If not |
.l |
A list of lists. The length of |
Note that arguments to be vectorised over come before the .f
,
and arguments that are supplied to every call come after .f
.
An atomic vector, list, or data frame, depending on the suffix.
Atomic vectors and lists will be named if .x
or the first
element of .l
is named.
If all input is length 0, the output will be length 0. If any input is length 1, it will be recycled to the length of the longest.
Other map variants: imap
,
invoke
, lmap
,
map
, modify
x <- list(1, 10, 100) y <- list(1, 2, 3) z <- list(5, 50, 500) map2(x, y, ~ .x + .y) # Or just map2(x, y, `+`) # Split into pieces, fit model to each piece, then predict by_cyl <- mtcars %>% split(.$cyl) mods <- by_cyl %>% map(~ lm(mpg ~ wt, data = .)) map2(mods, by_cyl, predict) pmap(list(x, y, z), sum) # Matching arguments by position pmap(list(x, y, z), function(a, b ,c) a / (b + c)) # Matching arguments by name l <- list(a = x, b = y, c = z) pmap(l, function(c, b, a) a / (b + c)) # Vectorizing a function over multiple arguments df <- data.frame( x = c("apple", "banana", "cherry"), pattern = c("p", "n", "h"), replacement = c("x", "f", "q"), stringsAsFactors = FALSE ) pmap(df, gsub) pmap_chr(df, gsub) ## Use `...` to absorb unused components of input list .l df <- data.frame( x = 1:3 + 0.1, y = 3:1 - 0.1, z = letters[1:3] ) plus <- function(x, y) x + y ## Not run: ## this won't work pmap(df, plus) ## End(Not run) ## but this will plus2 <- function(x, y, ...) x + y pmap_dbl(df, plus2)