rpurrr

how to keep named but 0-row tibbles in a list with list_rbind?

Let's say I have a list with named elements. The elements are tibbles. I would like to convert the list into one single tibble.

purrr's list_rbind works, with the critical shortcoming (at least for my purpose) that it drops the element which is a 0-row tibble (although it is a named element).

library(tidyverse)

li <- list("a"=tibble(x=1), "b"=tibble(x=2), "c"=tibble(x=NULL))
li
#> $a
#> # A tibble: 1 × 1
#>       x
#>   <dbl>
#> 1     1
#> 
#> $b
#> # A tibble: 1 × 1
#>       x
#>   <dbl>
#> 1     2
#> 
#> $c
#> # A tibble: 0 × 0


li %>% purrr::list_rbind(., names_to="element_names")

#> # A tibble: 2 × 2
#>   element_names     x
#>   <chr>         <dbl>
#> 1 a                 1
#> 2 b                 2

The outcome I am looking for would be

#>   element_names     x
#>   <chr>         <dbl>
#> 1 a                 1
#> 2 b                 2
#> 3 c                 NA (or NULL?)

Any help? Many thanks.

Solution

  • You can use enframe() and unnest():

    library(tibble)
library(tidyr)

enframe(li, name = "element_names")  |>
  unnest(value, keep_empty = TRUE)

# A tibble: 3 × 2
  element_names     x
  <chr>         <dbl>
1 a                 1
2 b                 2
3 c                NA