How to erase all attributes?

Question

I want to erase all attributes from data and applied this solution. However neither one_entry() (the original) nor my one_entry2() will work and I don't see why.

one_entry2 <- function(x) {
  attr(x, "label") <- NULL
  attr(x, "labels") <- NULL
}

> lapply(df1, one_entry2)
$`id`
NULL

$V1
NULL

$V2
NULL

$V3
NULL

How can we do this?

Data:

df1 <- setNames(data.frame(matrix(1:12, 3, 4)), 
                c("id", paste0("V", 1:3)))
attr(df1$V1, "labels") <- LETTERS[1:4]
attr(df1$V1, "label") <- letters[1:4]
attr(df1$V2, "labels") <- LETTERS[1:4]
attr(df1$V2, "label") <- letters[1:4]
attr(df1$V3, "labels") <- LETTERS[1:4]
attr(df1$V3, "label") <- letters[1:4]

> str(df1)
'data.frame':   3 obs. of  4 variables:
 $ id: int  1 2 3
 $ V1: int  4 5 6
  ..- attr(*, "labels")= chr  "A" "B" "C" "D"
  ..- attr(*, "label")= chr  "a" "b" "c" "d"
 $ V2: int  7 8 9
  ..- attr(*, "labels")= chr  "A" "B" "C" "D"
  ..- attr(*, "label")= chr  "a" "b" "c" "d"
 $ V3: int  10 11 12
  ..- attr(*, "labels")= chr  "A" "B" "C" "D"
  ..- attr(*, "label")= chr  "a" "b" "c" "d"

Answer 1

Simplifying a bit @maurits-evers answer:

df1[] <- lapply(df1, as.vector)
str(df1)
#'data.frame':  3 obs. of  4 variables:
# $ id: int  1 2 3
# $ V1: int  4 5 6
# $ V2: int  7 8 9
# $ V3: int  10 11 12

(The original answer is by Prof. Brian Ripley in https://r.789695.n4.nabble.com/function-to-remove-attributes-td914615.html)

In tidyverse world:

df1 <- df1 %>% mutate(across(everything(), as.vector))

With data.table

library(data.table)
# Assuming
# setDT(df1) # or
# df1 <- as.data.table(df1)

df1 <- df1[, lapply(.SD, as.vector)] 

Answer 2

To remove all attributes, how about this

df1[] <- lapply(df1, function(x) { attributes(x) <- NULL; x })
str(df1)
#'data.frame':  3 obs. of  4 variables:
# $ id: int  1 2 3
# $ V1: int  4 5 6
# $ V2: int  7 8 9
# $ V3: int  10 11 12

Answer 3

Provided all the columns are the same type (as in your example) you can do

df1[] = c(df1, recursive=TRUE)