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Find leaves satisfying predicate

Source: R/13_list_flattern.R
list_find.Rd

Find leaves satisfying predicate

Usage

list_find(.x, .p)

Arguments

.x

A nested list to traverse.

Lists are traversed recursively. Non-list objects are treated as leaves. Data frames are not traversed and are treated as leaf values.

.p

A predicate function, formula, or function-like object coercible by rlang::as_function().

Value

A flat list containing the leaf values of x for which .p returns TRUE.

The names of the returned list correspond to the flattened paths of the matching leaves.

See also

list_flatten()

Examples

x <- list(
  a = 1,
  b = list(
    x = 2,
    y = list(i = 3, j = 4)
  ),
  unnamed = list(5, z = 6)
)
list_find(x, ~ .x > 2 & .x < 5)
#> $b.y.i
#> [1] 3
#> 
#> $b.y.j
#> [1] 4
#> 
# $b.y.i
# [1] 3
#
# $b.y.j
# [1] 4

# Use a regular function
list_find(x, function(value) value %% 2 == 0)
#> $b.x
#> [1] 2
#> 
#> $b.y.j
#> [1] 4
#> 
#> $unnamed.z
#> [1] 6
#> 

# Non-TRUE predicate results are not kept
list_find(x, ~ NA)
#> named list()