在 R 中使用来自另一个列表的名称和值创建列表

Question

So the question is formunlated really badly, but what I want to achieve is the following: I have the following list:

list(a = data.frame(foo=1:10, bar=11:20), b = data.frame(foo=1:10, bar=11:20))

what I now want to create is another list that has the content as:

(list(a=c("foo", "bar"), b=c("foo", "bar")))
$a
[1] "foo" "bar"

$b
[1] "foo" "bar"

But obviously I don't want to hardcode it. I guess there is some more or less easy answer, but I just can't think of any at the moment. Named list and assigning names to objects still confuses me a lot in R. So any help would be super appreciated:)

Answer 1

Assuming your original list is "l", you can do:

lapply(l, names)
# $a
# [1] "foo" "bar"
# 
# $b
# [1] "foo" "bar"

From ?names , you get the description: "Functions to get or set the names of an object."

The names of the data.frame s in your original list are extracted with this, and lapply preserves the names of the original list.

Answer 2

An option with tidyverse

library(purrr)
map(l, names)

-output

#$a
#[1] "foo" "bar"

#$b
#[1] "foo" "bar"