Unnest a list column directly into several columns

Question

Can I unnest a list column directly into n columns?

The list can be assumed to regular, with all elements being of equal length.

If instead of a list column I would have a character vector, I could tidyr::separate. I can tidyr::unnest, but we need another helper variable to be able to tidyr::spread. Am I missing an obvious method?

Example data:

library(tibble)  df1 <- data_frame(   gr = c('a', 'b', 'c'),   values = list(1:2, 3:4, 5:6) ) 

# A tibble: 3 x 2   gr    values      <chr> <list>    1 a     <int [2]> 2 b     <int [2]> 3 c     <int [2]> 

Goal:

df2 <- data_frame(   gr = c('a', 'b', 'c'),   V1 = c(1, 3, 5),   V2 = c(2, 4, 6) ) 

# A tibble: 3 x 3   gr       V1    V2   <chr> <dbl> <dbl> 1 a        1.    2. 2 b        3.    4. 3 c        5.    6. 

Current method:

unnest(df1) %>%    group_by(gr) %>%    mutate(r = paste0('V', row_number())) %>%    spread(r, values) 

Answer 1

with tidyr 1.0.0 you can do :

library(tidyr) df1 <- tibble(   gr = c('a', 'b', 'c'),   values = list(1:2, 3:4, 5:6) )  unnest_wider(df1, values) #> New names: #> * `` -> ...1 #> * `` -> ...2 #> New names: #> * `` -> ...1 #> * `` -> ...2 #> New names: #> * `` -> ...1 #> * `` -> ...2 #> # A tibble: 3 x 3 #>   gr     ...1  ...2 #>   <chr> <int> <int> #> 1 a         1     2 #> 2 b         3     4 #> 3 c         5     6 

^{Created on 2019-09-14 by the reprex package (v0.3.0)}

The output is verbose here because the elements that were unnested horizontally (the vector elements) were not named, and unnest_wider doesn't want to guess silently.

We can name them beforehand to avoid it :

df1 %>%   dplyr::mutate(values = purrr::map(values, setNames, c("V1","V2"))) %>%   unnest_wider(values) #> # A tibble: 3 x 3 #>   gr       V1    V2 #>   <chr> <int> <int> #> 1 a         1     2 #> 2 b         3     4 #> 3 c         5     6 

Or just use suppressMessages() or purrr::quietly()