Modify a pluck location

• assign_in() takes a data structure and a pluck location, assigns a value there, and returns the modified data structure.

• modify_in() applies a function to a pluck location, assigns the result back to that location with assign_in(), and returns the modified data structure.

The pluck location must exist.

modify_in(.x, .where, .f, ...)

assign_in(x, where, value)

Arguments

.x	A vector or environment
.where, where	A pluck location, as a numeric vector of positions, a character vector of names, or a list combining both. The location must exist in the data structure.
.f	A function to apply at the pluck location given by .where.
...	Arguments passed to .f.
x	A vector or environment
value	A value to replace in .x at the pluck location.

See also

pluck()

Examples

# Recall that pluck() returns a component of a data structure that
# might be arbitrarily deep
x <- list(list(bar = 1, foo = 2))
pluck(x, 1, "foo")
#> [1] 2

# Use assign_in() to modify the pluck location:
assign_in(x, list(1, "foo"), 100)
#> [[1]]
#> [[1]]$bar
#> [1] 1
#> 
#> [[1]]$foo
#> [1] 100
#> 
#> 

# modify_in() applies a function to that location and update the
# element in place:
modify_in(x, list(1, "foo"), ~ .x * 200)
#> [[1]]
#> [[1]]$bar
#> [1] 1
#> 
#> [[1]]$foo
#> [1] 400
#> 
#> 

# Additional arguments are passed to the function in the ordinary way:
modify_in(x, list(1, "foo"), `+`, 100)
#> [[1]]
#> [[1]]$bar
#> [1] 1
#> 
#> [[1]]$foo
#> [1] 102
#> 
#>