Set a nested element by path

Set a nested element by path

Usage

list_set(x, path, value)

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.

path

Character or integer vector giving the path to retrieve.

For a character path, each component selects a named element at the current level. For an integer path, each component selects an element by position. Positional indices are one-based, following normal R indexing conventions.

The path is evaluated from left to right. For example, c("b", "y", "i") means x[["b"]][["y"]][["i"]].

value

Value to set at path.

This value replaces the existing element located at path. It may be any R object.

Value

A modified copy of x with value assigned at path.

See also

list_get(), list_has()

Other lstrrr_core: list_delete(), list_depth(), list_get(), list_has(), list_nleaf(), list_path()

Examples

x <- list(
  a = 1,
  b = list(
    x = 1,
    y = list(i = 1, j = 2)
  )
)

list_set(x, c("b", "x"), 2)
#> $a
#> [1] 1
#> 
#> $b
#> $b$x
#> [1] 2
#> 
#> $b$y
#> $b$y$i
#> [1] 1
#> 
#> $b$y$j
#> [1] 2
#> 
#> 
#> 

# Set a deeply nested value
list_set(x, c("b", "y", "i"), 100)
#> $a
#> [1] 1
#> 
#> $b
#> $b$x
#> [1] 1
#> 
#> $b$y
#> $b$y$i
#> [1] 100
#> 
#> $b$y$j
#> [1] 2
#> 
#> 
#> 

# Integer paths use positional indices
list_set(x, c(2L, 2L, 2L), 200)
#> [[1]]
#> [1] 1
#> 
#> [[2]]
#> [[2]][[1]]
#> [1] 1
#> 
#> [[2]][[2]]
#> [[2]][[2]][[1]]
#> [1] 1
#> 
#> [[2]][[2]][[2]]
#> [1] 200
#> 
#> 
#> 

# Empty path replaces the whole object
list_set(x, character(0), "replacement")
#> [1] "replacement"

# The original object is unchanged unless reassigned
x2 <- list_set(x, c("b", "x"), 2)
x$b$x
#> [1] 1
x2$b$x
#> [1] 2