Return a table applying a function to all combinations of list elements

Return a table applying a function to all combinations of list elements

Usage

xmap_mat(.l, .f, ..., .names = TRUE)

xmap_arr(.l, .f, ..., .names = TRUE)

Arguments

.l

A list of vectors, such as a data frame. The length of .l determines the number of arguments that .f will be called with. List names will be used if present.

.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 .f

.names

A logical indicating whether to give names to the dimensions of the matrix or array. If inputs are named, the names are used. If inputs are unnamed, the elements of the input are used as names. Defaults to TRUE.

Value

A matrix (for xmap_mat()) or array (for xmap_arr()) with dimensions equal to the lengths of each input in .l.

See also

future_xmap_mat() and future_xmap_arr() to run functions in parallel.

xmap_vec() to return a vector.

xmap() for the underlying functions.

Examples

xmap_mat(list(1:3, 1:3),  ~ ..1 * ..2)
#>   1 2 3
#> 1 1 2 3
#> 2 2 4 6
#> 3 3 6 9

fruits <- c(a = "apple", b = "banana", c = "cantaloupe")
xmap_mat(list(1:3, fruits), paste)
#>   a         b          c             
#> 1 "1 apple" "1 banana" "1 cantaloupe"
#> 2 "2 apple" "2 banana" "2 cantaloupe"
#> 3 "3 apple" "3 banana" "3 cantaloupe"
xmap_mat(list(1:3, fruits), paste, .names = FALSE)
#>      [,1]      [,2]       [,3]          
#> [1,] "1 apple" "1 banana" "1 cantaloupe"
#> [2,] "2 apple" "2 banana" "2 cantaloupe"
#> [3,] "3 apple" "3 banana" "3 cantaloupe"

xmap_arr(list(1:3, 1:3, 1:3),  ~ ..1 * ..2 * ..3)
#> , , 1
#> 
#>   1 2 3
#> 1 1 2 3
#> 2 2 4 6
#> 3 3 6 9
#> 
#> , , 2
#> 
#>   1  2  3
#> 1 2  4  6
#> 2 4  8 12
#> 3 6 12 18
#> 
#> , , 3
#> 
#>   1  2  3
#> 1 3  6  9
#> 2 6 12 18
#> 3 9 18 27
#>