R purrr modify_in 修改拔取位置

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

assign_in(x, where, value)

pluck()

# 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:
str(assign_in(x, list(1, "foo"), 100))
#> List of 1
#>  $ :List of 2
#>   ..$ bar: num 1
#>   ..$ foo: num 100
# Or zap to remove it
str(assign_in(x, list(1, "foo"), zap()))
#> List of 1
#>  $ :List of 1
#>   ..$ bar: num 1

# Like pluck(), this works even when the element (or its parents) don't exist
pluck(x, 1, "baz")
#> NULL
str(assign_in(x, list(2, "baz"), 100))
#> List of 2
#>  $ :List of 2
#>   ..$ bar: num 1
#>   ..$ foo: num 2
#>  $ :List of 1
#>   ..$ baz: num 100

# modify_in() applies a function to that location and update the
# element in place:
modify_in(x, list(1, "foo"), \(x) 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
#> 
#>