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rvectornested

Apply function to a certain element of a nested list

I want to substract one from a particular element of a nested list. How should I do that?

This is my nested list I want to one from positive values of bar vector (check first is it is positive)

x <- list(a = list(foo = 1:8, bar = 3:4), b = list(baz = 5:6))

I was thinking about map function.

Thank you!

Solution

  • You could write a recursive function:

    mod_at <- function(x, name, FUN){
  if(name %in% names(x)){ 
    x[[name]] <- FUN(x[[name]])
    x
  }
  else if(is.list(x))lapply(x, mod_at, name, FUN)
  else x
}

    Now use that to modify the list:

    mod_at(x, "bar", function(x)ifelse(x>0, x-1, x))

$a
$a$foo
[1] 1 2 3 4 5 6 7 8

$a$bar
[1] 2 3


$b
$b$baz
[1] 5 6

    You could use the function the way you want:

    mod_at(x, "baz", sqrt)

$a
$a$foo
[1] 1 2 3 4 5 6 7 8

$a$bar
[1] 3 4


$b
$b$baz
[1] 2.236068 2.449490