Keep/discard elements based on their name/position

keep_at() and discard_at() are similar to [ or dplyr::select(): they return the same type of data structure as the input, but only containing the requested elements. (If you're looking for a function similar to [[ see pluck()/chuck()).

Usage

keep_at(x, at)

discard_at(x, at)

Arguments

x

A list or atomic vector.

at

A logical, integer, or character vector giving the elements to select. Alternatively, a function that takes a vector of names, and returns a logical, integer, or character vector of elements to select.

See also

keep()/discard() to keep/discard elements by value.

Examples

x <- c(a = 1, b = 2, cat = 10, dog = 15, elephant = 5, e = 10)
x |> keep_at(letters)
#>  a  b  e 
#>  1  2 10 
x |> discard_at(letters)
#>      cat      dog elephant 
#>       10       15        5 

# Can also use a function
x |> keep_at(\(x) nchar(x) == 3)
#> cat dog 
#>  10  15 
x |> discard_at(\(x) nchar(x) == 3)
#>        a        b elephant        e 
#>        1        2        5       10