Apply a function to each element of a vector conditionally

Source: R/map.R

The functions map_if() and map_at() take .x as input, apply the function .f to some of the elements of .x, and return a list of the same length as the input.

  • map_if() takes a predicate function .p as input to determine which elements of .x are transformed with .f.

  • map_at() takes a vector of names or positions .at to specify which elements of .x are transformed with .f.

  • map_depth() allows to apply .f to a specific depth level of a nested vector.

map_if(.x, .p, .f, ..., .else = NULL)

map_at(.x, .at, .f, ...)

map_depth(.x, .depth, .f, ..., .ragged = FALSE)

Arguments

.x

A list or atomic vector.
.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.
.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.
.else

A function applied to elements of .x for which .p returns FALSE.
.at

A character vector of names, positive numeric vector of positions to include, or a negative numeric vector of positions to exlude. Only those elements corresponding to .at will be modified. If the tidyselect package is installed, you can use vars() and the tidyselect helpers to select elements.
.depth

Level of .x to map on. Use a negative value to count up from the lowest level of the list.

  • map_depth(x, 0, fun) is equivalent to fun(x).

  • map_depth(x, 1, fun) is equivalent to x <- map(x, fun)

  • map_depth(x, 2, fun) is equivalent to x <- map(x, ~ map(., fun))
.ragged

If TRUE, will apply to leaves, even if they're not at depth .depth. If FALSE, will throw an error if there are no elements at depth .depth.

See also

Other map variants: imap(), invoke(), lmap(), map2(), map(), modify()

Examples

# Use a predicate function to decide whether to map a function:
map_if(iris, is.factor, as.character)
#> $Sepal.Length
#>   [1] 5.1 4.9 4.7 4.6 5.0 5.4 4.6 5.0 4.4 4.9 5.4 4.8 4.8 4.3 5.8 5.7 5.4 5.1
#>  [19] 5.7 5.1 5.4 5.1 4.6 5.1 4.8 5.0 5.0 5.2 5.2 4.7 4.8 5.4 5.2 5.5 4.9 5.0
#>  [37] 5.5 4.9 4.4 5.1 5.0 4.5 4.4 5.0 5.1 4.8 5.1 4.6 5.3 5.0 7.0 6.4 6.9 5.5
#>  [55] 6.5 5.7 6.3 4.9 6.6 5.2 5.0 5.9 6.0 6.1 5.6 6.7 5.6 5.8 6.2 5.6 5.9 6.1
#>  [73] 6.3 6.1 6.4 6.6 6.8 6.7 6.0 5.7 5.5 5.5 5.8 6.0 5.4 6.0 6.7 6.3 5.6 5.5
#>  [91] 5.5 6.1 5.8 5.0 5.6 5.7 5.7 6.2 5.1 5.7 6.3 5.8 7.1 6.3 6.5 7.6 4.9 7.3
#> [109] 6.7 7.2 6.5 6.4 6.8 5.7 5.8 6.4 6.5 7.7 7.7 6.0 6.9 5.6 7.7 6.3 6.7 7.2
#> [127] 6.2 6.1 6.4 7.2 7.4 7.9 6.4 6.3 6.1 7.7 6.3 6.4 6.0 6.9 6.7 6.9 5.8 6.8
#> [145] 6.7 6.7 6.3 6.5 6.2 5.9
#> 
#> $Sepal.Width
#>   [1] 3.5 3.0 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 3.7 3.4 3.0 3.0 4.0 4.4 3.9 3.5
#>  [19] 3.8 3.8 3.4 3.7 3.6 3.3 3.4 3.0 3.4 3.5 3.4 3.2 3.1 3.4 4.1 4.2 3.1 3.2
#>  [37] 3.5 3.6 3.0 3.4 3.5 2.3 3.2 3.5 3.8 3.0 3.8 3.2 3.7 3.3 3.2 3.2 3.1 2.3
#>  [55] 2.8 2.8 3.3 2.4 2.9 2.7 2.0 3.0 2.2 2.9 2.9 3.1 3.0 2.7 2.2 2.5 3.2 2.8
#>  [73] 2.5 2.8 2.9 3.0 2.8 3.0 2.9 2.6 2.4 2.4 2.7 2.7 3.0 3.4 3.1 2.3 3.0 2.5
#>  [91] 2.6 3.0 2.6 2.3 2.7 3.0 2.9 2.9 2.5 2.8 3.3 2.7 3.0 2.9 3.0 3.0 2.5 2.9
#> [109] 2.5 3.6 3.2 2.7 3.0 2.5 2.8 3.2 3.0 3.8 2.6 2.2 3.2 2.8 2.8 2.7 3.3 3.2
#> [127] 2.8 3.0 2.8 3.0 2.8 3.8 2.8 2.8 2.6 3.0 3.4 3.1 3.0 3.1 3.1 3.1 2.7 3.2
#> [145] 3.3 3.0 2.5 3.0 3.4 3.0
#> 
#> $Petal.Length
#>   [1] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 1.5 1.6 1.4 1.1 1.2 1.5 1.3 1.4
#>  [19] 1.7 1.5 1.7 1.5 1.0 1.7 1.9 1.6 1.6 1.5 1.4 1.6 1.6 1.5 1.5 1.4 1.5 1.2
#>  [37] 1.3 1.4 1.3 1.5 1.3 1.3 1.3 1.6 1.9 1.4 1.6 1.4 1.5 1.4 4.7 4.5 4.9 4.0
#>  [55] 4.6 4.5 4.7 3.3 4.6 3.9 3.5 4.2 4.0 4.7 3.6 4.4 4.5 4.1 4.5 3.9 4.8 4.0
#>  [73] 4.9 4.7 4.3 4.4 4.8 5.0 4.5 3.5 3.8 3.7 3.9 5.1 4.5 4.5 4.7 4.4 4.1 4.0
#>  [91] 4.4 4.6 4.0 3.3 4.2 4.2 4.2 4.3 3.0 4.1 6.0 5.1 5.9 5.6 5.8 6.6 4.5 6.3
#> [109] 5.8 6.1 5.1 5.3 5.5 5.0 5.1 5.3 5.5 6.7 6.9 5.0 5.7 4.9 6.7 4.9 5.7 6.0
#> [127] 4.8 4.9 5.6 5.8 6.1 6.4 5.6 5.1 5.6 6.1 5.6 5.5 4.8 5.4 5.6 5.1 5.1 5.9
#> [145] 5.7 5.2 5.0 5.2 5.4 5.1
#> 
#> $Petal.Width
#>   [1] 0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 0.2 0.2 0.1 0.1 0.2 0.4 0.4 0.3
#>  [19] 0.3 0.3 0.2 0.4 0.2 0.5 0.2 0.2 0.4 0.2 0.2 0.2 0.2 0.4 0.1 0.2 0.2 0.2
#>  [37] 0.2 0.1 0.2 0.2 0.3 0.3 0.2 0.6 0.4 0.3 0.2 0.2 0.2 0.2 1.4 1.5 1.5 1.3
#>  [55] 1.5 1.3 1.6 1.0 1.3 1.4 1.0 1.5 1.0 1.4 1.3 1.4 1.5 1.0 1.5 1.1 1.8 1.3
#>  [73] 1.5 1.2 1.3 1.4 1.4 1.7 1.5 1.0 1.1 1.0 1.2 1.6 1.5 1.6 1.5 1.3 1.3 1.3
#>  [91] 1.2 1.4 1.2 1.0 1.3 1.2 1.3 1.3 1.1 1.3 2.5 1.9 2.1 1.8 2.2 2.1 1.7 1.8
#> [109] 1.8 2.5 2.0 1.9 2.1 2.0 2.4 2.3 1.8 2.2 2.3 1.5 2.3 2.0 2.0 1.8 2.1 1.8
#> [127] 1.8 1.8 2.1 1.6 1.9 2.0 2.2 1.5 1.4 2.3 2.4 1.8 1.8 2.1 2.4 2.3 1.9 2.3
#> [145] 2.5 2.3 1.9 2.0 2.3 1.8
#> 
#> $Species
#>   [1] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>   [6] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [11] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [16] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [21] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [26] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [31] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [36] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [41] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [46] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [51] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [56] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [61] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [66] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [71] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [76] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [81] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [86] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [91] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [96] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#> [101] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [106] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [111] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [116] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [121] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [126] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [131] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [136] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [141] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [146] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> 

# Specify an alternative with the `.else` argument:
map_if(iris, is.factor, as.character, .else = as.integer)
#> $Sepal.Length
#>   [1] 5 4 4 4 5 5 4 5 4 4 5 4 4 4 5 5 5 5 5 5 5 5 4 5 4 5 5 5 5 4 4 5 5 5 4 5 5
#>  [38] 4 4 5 5 4 4 5 5 4 5 4 5 5 7 6 6 5 6 5 6 4 6 5 5 5 6 6 5 6 5 5 6 5 5 6 6 6
#>  [75] 6 6 6 6 6 5 5 5 5 6 5 6 6 6 5 5 5 6 5 5 5 5 5 6 5 5 6 5 7 6 6 7 4 7 6 7 6
#> [112] 6 6 5 5 6 6 7 7 6 6 5 7 6 6 7 6 6 6 7 7 7 6 6 6 7 6 6 6 6 6 6 5 6 6 6 6 6
#> [149] 6 5
#> 
#> $Sepal.Width
#>   [1] 3 3 3 3 3 3 3 3 2 3 3 3 3 3 4 4 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 4 4 3 3 3
#>  [38] 3 3 3 3 2 3 3 3 3 3 3 3 3 3 3 3 2 2 2 3 2 2 2 2 3 2 2 2 3 3 2 2 2 3 2 2 2
#>  [75] 2 3 2 3 2 2 2 2 2 2 3 3 3 2 3 2 2 3 2 2 2 3 2 2 2 2 3 2 3 2 3 3 2 2 2 3 3
#> [112] 2 3 2 2 3 3 3 2 2 3 2 2 2 3 3 2 3 2 3 2 3 2 2 2 3 3 3 3 3 3 3 2 3 3 3 2 3
#> [149] 3 3
#> 
#> $Petal.Length
#>   [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
#>  [38] 1 1 1 1 1 1 1 1 1 1 1 1 1 4 4 4 4 4 4 4 3 4 3 3 4 4 4 3 4 4 4 4 3 4 4 4 4
#>  [75] 4 4 4 5 4 3 3 3 3 5 4 4 4 4 4 4 4 4 4 3 4 4 4 4 3 4 6 5 5 5 5 6 4 6 5 6 5
#> [112] 5 5 5 5 5 5 6 6 5 5 4 6 4 5 6 4 4 5 5 6 6 5 5 5 6 5 5 4 5 5 5 5 5 5 5 5 5
#> [149] 5 5
#> 
#> $Petal.Width
#>   [1] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
#>  [38] 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
#>  [75] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 2 1 2 2 1 1 1 2 2
#> [112] 1 2 2 2 2 1 2 2 1 2 2 2 1 2 1 1 1 2 1 1 2 2 1 1 2 2 1 1 2 2 2 1 2 2 2 1 2
#> [149] 2 1
#> 
#> $Species
#>   [1] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>   [6] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [11] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [16] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [21] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [26] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [31] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [36] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [41] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [46] "setosa"     "setosa"     "setosa"     "setosa"     "setosa"    
#>  [51] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [56] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [61] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [66] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [71] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [76] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [81] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [86] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [91] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#>  [96] "versicolor" "versicolor" "versicolor" "versicolor" "versicolor"
#> [101] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [106] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [111] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [116] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [121] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [126] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [131] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [136] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [141] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> [146] "virginica"  "virginica"  "virginica"  "virginica"  "virginica" 
#> 

# Use numeric vector of positions select elements to change:
iris %>% map_at(c(4, 5), is.numeric)
#> $Sepal.Length
#>   [1] 5.1 4.9 4.7 4.6 5.0 5.4 4.6 5.0 4.4 4.9 5.4 4.8 4.8 4.3 5.8 5.7 5.4 5.1
#>  [19] 5.7 5.1 5.4 5.1 4.6 5.1 4.8 5.0 5.0 5.2 5.2 4.7 4.8 5.4 5.2 5.5 4.9 5.0
#>  [37] 5.5 4.9 4.4 5.1 5.0 4.5 4.4 5.0 5.1 4.8 5.1 4.6 5.3 5.0 7.0 6.4 6.9 5.5
#>  [55] 6.5 5.7 6.3 4.9 6.6 5.2 5.0 5.9 6.0 6.1 5.6 6.7 5.6 5.8 6.2 5.6 5.9 6.1
#>  [73] 6.3 6.1 6.4 6.6 6.8 6.7 6.0 5.7 5.5 5.5 5.8 6.0 5.4 6.0 6.7 6.3 5.6 5.5
#>  [91] 5.5 6.1 5.8 5.0 5.6 5.7 5.7 6.2 5.1 5.7 6.3 5.8 7.1 6.3 6.5 7.6 4.9 7.3
#> [109] 6.7 7.2 6.5 6.4 6.8 5.7 5.8 6.4 6.5 7.7 7.7 6.0 6.9 5.6 7.7 6.3 6.7 7.2
#> [127] 6.2 6.1 6.4 7.2 7.4 7.9 6.4 6.3 6.1 7.7 6.3 6.4 6.0 6.9 6.7 6.9 5.8 6.8
#> [145] 6.7 6.7 6.3 6.5 6.2 5.9
#> 
#> $Sepal.Width
#>   [1] 3.5 3.0 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 3.7 3.4 3.0 3.0 4.0 4.4 3.9 3.5
#>  [19] 3.8 3.8 3.4 3.7 3.6 3.3 3.4 3.0 3.4 3.5 3.4 3.2 3.1 3.4 4.1 4.2 3.1 3.2
#>  [37] 3.5 3.6 3.0 3.4 3.5 2.3 3.2 3.5 3.8 3.0 3.8 3.2 3.7 3.3 3.2 3.2 3.1 2.3
#>  [55] 2.8 2.8 3.3 2.4 2.9 2.7 2.0 3.0 2.2 2.9 2.9 3.1 3.0 2.7 2.2 2.5 3.2 2.8
#>  [73] 2.5 2.8 2.9 3.0 2.8 3.0 2.9 2.6 2.4 2.4 2.7 2.7 3.0 3.4 3.1 2.3 3.0 2.5
#>  [91] 2.6 3.0 2.6 2.3 2.7 3.0 2.9 2.9 2.5 2.8 3.3 2.7 3.0 2.9 3.0 3.0 2.5 2.9
#> [109] 2.5 3.6 3.2 2.7 3.0 2.5 2.8 3.2 3.0 3.8 2.6 2.2 3.2 2.8 2.8 2.7 3.3 3.2
#> [127] 2.8 3.0 2.8 3.0 2.8 3.8 2.8 2.8 2.6 3.0 3.4 3.1 3.0 3.1 3.1 3.1 2.7 3.2
#> [145] 3.3 3.0 2.5 3.0 3.4 3.0
#> 
#> $Petal.Length
#>   [1] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 1.5 1.6 1.4 1.1 1.2 1.5 1.3 1.4
#>  [19] 1.7 1.5 1.7 1.5 1.0 1.7 1.9 1.6 1.6 1.5 1.4 1.6 1.6 1.5 1.5 1.4 1.5 1.2
#>  [37] 1.3 1.4 1.3 1.5 1.3 1.3 1.3 1.6 1.9 1.4 1.6 1.4 1.5 1.4 4.7 4.5 4.9 4.0
#>  [55] 4.6 4.5 4.7 3.3 4.6 3.9 3.5 4.2 4.0 4.7 3.6 4.4 4.5 4.1 4.5 3.9 4.8 4.0
#>  [73] 4.9 4.7 4.3 4.4 4.8 5.0 4.5 3.5 3.8 3.7 3.9 5.1 4.5 4.5 4.7 4.4 4.1 4.0
#>  [91] 4.4 4.6 4.0 3.3 4.2 4.2 4.2 4.3 3.0 4.1 6.0 5.1 5.9 5.6 5.8 6.6 4.5 6.3
#> [109] 5.8 6.1 5.1 5.3 5.5 5.0 5.1 5.3 5.5 6.7 6.9 5.0 5.7 4.9 6.7 4.9 5.7 6.0
#> [127] 4.8 4.9 5.6 5.8 6.1 6.4 5.6 5.1 5.6 6.1 5.6 5.5 4.8 5.4 5.6 5.1 5.1 5.9
#> [145] 5.7 5.2 5.0 5.2 5.4 5.1
#> 
#> $Petal.Width
#> [1] TRUE
#> 
#> $Species
#> [1] FALSE
#> 

# Use vector of names to specify which elements to change:
iris %>% map_at("Species", toupper)
#> $Sepal.Length
#>   [1] 5.1 4.9 4.7 4.6 5.0 5.4 4.6 5.0 4.4 4.9 5.4 4.8 4.8 4.3 5.8 5.7 5.4 5.1
#>  [19] 5.7 5.1 5.4 5.1 4.6 5.1 4.8 5.0 5.0 5.2 5.2 4.7 4.8 5.4 5.2 5.5 4.9 5.0
#>  [37] 5.5 4.9 4.4 5.1 5.0 4.5 4.4 5.0 5.1 4.8 5.1 4.6 5.3 5.0 7.0 6.4 6.9 5.5
#>  [55] 6.5 5.7 6.3 4.9 6.6 5.2 5.0 5.9 6.0 6.1 5.6 6.7 5.6 5.8 6.2 5.6 5.9 6.1
#>  [73] 6.3 6.1 6.4 6.6 6.8 6.7 6.0 5.7 5.5 5.5 5.8 6.0 5.4 6.0 6.7 6.3 5.6 5.5
#>  [91] 5.5 6.1 5.8 5.0 5.6 5.7 5.7 6.2 5.1 5.7 6.3 5.8 7.1 6.3 6.5 7.6 4.9 7.3
#> [109] 6.7 7.2 6.5 6.4 6.8 5.7 5.8 6.4 6.5 7.7 7.7 6.0 6.9 5.6 7.7 6.3 6.7 7.2
#> [127] 6.2 6.1 6.4 7.2 7.4 7.9 6.4 6.3 6.1 7.7 6.3 6.4 6.0 6.9 6.7 6.9 5.8 6.8
#> [145] 6.7 6.7 6.3 6.5 6.2 5.9
#> 
#> $Sepal.Width
#>   [1] 3.5 3.0 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 3.7 3.4 3.0 3.0 4.0 4.4 3.9 3.5
#>  [19] 3.8 3.8 3.4 3.7 3.6 3.3 3.4 3.0 3.4 3.5 3.4 3.2 3.1 3.4 4.1 4.2 3.1 3.2
#>  [37] 3.5 3.6 3.0 3.4 3.5 2.3 3.2 3.5 3.8 3.0 3.8 3.2 3.7 3.3 3.2 3.2 3.1 2.3
#>  [55] 2.8 2.8 3.3 2.4 2.9 2.7 2.0 3.0 2.2 2.9 2.9 3.1 3.0 2.7 2.2 2.5 3.2 2.8
#>  [73] 2.5 2.8 2.9 3.0 2.8 3.0 2.9 2.6 2.4 2.4 2.7 2.7 3.0 3.4 3.1 2.3 3.0 2.5
#>  [91] 2.6 3.0 2.6 2.3 2.7 3.0 2.9 2.9 2.5 2.8 3.3 2.7 3.0 2.9 3.0 3.0 2.5 2.9
#> [109] 2.5 3.6 3.2 2.7 3.0 2.5 2.8 3.2 3.0 3.8 2.6 2.2 3.2 2.8 2.8 2.7 3.3 3.2
#> [127] 2.8 3.0 2.8 3.0 2.8 3.8 2.8 2.8 2.6 3.0 3.4 3.1 3.0 3.1 3.1 3.1 2.7 3.2
#> [145] 3.3 3.0 2.5 3.0 3.4 3.0
#> 
#> $Petal.Length
#>   [1] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 1.5 1.6 1.4 1.1 1.2 1.5 1.3 1.4
#>  [19] 1.7 1.5 1.7 1.5 1.0 1.7 1.9 1.6 1.6 1.5 1.4 1.6 1.6 1.5 1.5 1.4 1.5 1.2
#>  [37] 1.3 1.4 1.3 1.5 1.3 1.3 1.3 1.6 1.9 1.4 1.6 1.4 1.5 1.4 4.7 4.5 4.9 4.0
#>  [55] 4.6 4.5 4.7 3.3 4.6 3.9 3.5 4.2 4.0 4.7 3.6 4.4 4.5 4.1 4.5 3.9 4.8 4.0
#>  [73] 4.9 4.7 4.3 4.4 4.8 5.0 4.5 3.5 3.8 3.7 3.9 5.1 4.5 4.5 4.7 4.4 4.1 4.0
#>  [91] 4.4 4.6 4.0 3.3 4.2 4.2 4.2 4.3 3.0 4.1 6.0 5.1 5.9 5.6 5.8 6.6 4.5 6.3
#> [109] 5.8 6.1 5.1 5.3 5.5 5.0 5.1 5.3 5.5 6.7 6.9 5.0 5.7 4.9 6.7 4.9 5.7 6.0
#> [127] 4.8 4.9 5.6 5.8 6.1 6.4 5.6 5.1 5.6 6.1 5.6 5.5 4.8 5.4 5.6 5.1 5.1 5.9
#> [145] 5.7 5.2 5.0 5.2 5.4 5.1
#> 
#> $Petal.Width
#>   [1] 0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 0.2 0.2 0.1 0.1 0.2 0.4 0.4 0.3
#>  [19] 0.3 0.3 0.2 0.4 0.2 0.5 0.2 0.2 0.4 0.2 0.2 0.2 0.2 0.4 0.1 0.2 0.2 0.2
#>  [37] 0.2 0.1 0.2 0.2 0.3 0.3 0.2 0.6 0.4 0.3 0.2 0.2 0.2 0.2 1.4 1.5 1.5 1.3
#>  [55] 1.5 1.3 1.6 1.0 1.3 1.4 1.0 1.5 1.0 1.4 1.3 1.4 1.5 1.0 1.5 1.1 1.8 1.3
#>  [73] 1.5 1.2 1.3 1.4 1.4 1.7 1.5 1.0 1.1 1.0 1.2 1.6 1.5 1.6 1.5 1.3 1.3 1.3
#>  [91] 1.2 1.4 1.2 1.0 1.3 1.2 1.3 1.3 1.1 1.3 2.5 1.9 2.1 1.8 2.2 2.1 1.7 1.8
#> [109] 1.8 2.5 2.0 1.9 2.1 2.0 2.4 2.3 1.8 2.2 2.3 1.5 2.3 2.0 2.0 1.8 2.1 1.8
#> [127] 1.8 1.8 2.1 1.6 1.9 2.0 2.2 1.5 1.4 2.3 2.4 1.8 1.8 2.1 2.4 2.3 1.9 2.3
#> [145] 2.5 2.3 1.9 2.0 2.3 1.8
#> 
#> $Species
#>   [1] "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"    
#>   [6] "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"    
#>  [11] "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"    
#>  [16] "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"    
#>  [21] "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"    
#>  [26] "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"    
#>  [31] "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"    
#>  [36] "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"    
#>  [41] "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"    
#>  [46] "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"     "SETOSA"    
#>  [51] "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR"
#>  [56] "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR"
#>  [61] "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR"
#>  [66] "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR"
#>  [71] "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR"
#>  [76] "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR"
#>  [81] "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR"
#>  [86] "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR"
#>  [91] "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR"
#>  [96] "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR" "VERSICOLOR"
#> [101] "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA" 
#> [106] "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA" 
#> [111] "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA" 
#> [116] "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA" 
#> [121] "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA" 
#> [126] "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA" 
#> [131] "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA" 
#> [136] "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA" 
#> [141] "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA" 
#> [146] "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA"  "VIRGINICA" 
#> 

# Use `map_depth()` to recursively traverse nested vectors and map
# a function at a certain depth:
x <- list(a = list(foo = 1:2, bar = 3:4), b = list(baz = 5:6))
str(x)
#> List of 2
#>  $ a:List of 2
#>   ..$ foo: int [1:2] 1 2
#>   ..$ bar: int [1:2] 3 4
#>  $ b:List of 1
#>   ..$ baz: int [1:2] 5 6
map_depth(x, 2, paste, collapse = "/")
#> $a
#> $a$foo
#> [1] "1/2"
#> 
#> $a$bar
#> [1] "3/4"
#> 
#> 
#> $b
#> $b$baz
#> [1] "5/6"
#> 
#> 

# Equivalent to:
map(x, map, paste, collapse = "/")
#> $a
#> $a$foo
#> [1] "1/2"
#> 
#> $a$bar
#> [1] "3/4"
#> 
#> 
#> $b
#> $b$baz
#> [1] "5/6"
#> 
#>