How to delete several elements from a list() at once in R?

Question

I have the following list:

x <- list("1", 1, 2, 2.1, TRUE, "yes", "necessary", 31, FALSE, "FALSE")

would like to exclude from it all the elements which NAY are whole numbers and not characters, in which case the elements which are in heading [4], [5] and [9] I’ve tried to make:

x <- x[-4][-5][-9]

however only the first element is removed correctly, so that the index of each later element is changed with the one removed from the first, the list is:

[[1]]
[1] "1"

[[2]]
[1] 1

[[3]]
[1] 2

[[4]]
[1] TRUE

[[5]]
[1] "necessary"

[[6]]
[1] 31

[[7]]
[1] FALSE

[[8]]
[1] "FALSE"

how to remove the items from position [4], [5] and [9] without changing the index of unwanted items?

Answer 1

To remove exactly positions 4, 5 and 9, just inform a vector with these positions to the list:

x <- list("1", 1, 2, 2.1, TRUE, "yes", "necessary", 31, FALSE, "FALSE")

x[-c(4, 5, 9)]
#> [[1]]
#> [1] "1"
#> 
#> [[2]]
#> [1] 1
#> 
#> [[3]]
#> [1] 2
#> 
#> [[4]]
#> [1] "yes"
#> 
#> [[5]]
#> [1] "necessary"
#> 
#> [[6]]
#> [1] 31
#> 
#> [[7]]
#> [1] "FALSE"

But if you want something more general that fits any situation where you want to delete from a list all elements that are not integer numbers or characters, use the solution below.

The function testar.inteiro checks that each element in the list is defined only as a number without a decimal part.

testar.inteiro <- function(x){
  !grepl("[^[:digit:]]", format(x, digits = options()$digits, scientific = FALSE))
}

x[!(!sapply(x, is.character) & !sapply(x, testar.inteiro))]
#> [[1]]
#> [1] "1"
#> 
#> [[2]]
#> [1] 1
#> 
#> [[3]]
#> [1] 2
#> 
#> [[4]]
#> [1] "yes"
#> 
#> [[5]]
#> [1] "necessary"
#> 
#> [[6]]
#> [1] 31
#> 
#> [[7]]
#> [1] "FALSE"

Note that in the original example, the first element of the list is "1", that for R is not an integer number. That is a character. However, the function testar.inteiro keeps this element in the list, because the question asked for it in its expected result,.