Unnest data.frames within fully named list

Consider a function that returns a list of two data.frames. Call that function repeatedly and store each return value in a list. You then hold a list of fully named lists, and each inner list holds a data.frame. Typically you want the two data.frames out of that nested structure, row-bound with data.table::rbindlist().

Usage

unnest_dfs_within_list_of_fully_named_lists(
  x,
  returned_name_when_dfs_are_not_nested = "data",
  ...
)

Arguments

x

A list of fully named lists (which then contain data.frames)

returned_name_when_dfs_are_not_nested

The name to give the returned element when x is a single list of data.frames.

...

Parameters passed to data.table::rbindlist().

Value

A fully named list, each element a data.table. NULL if x is not a list.

Details

When every element of x is NULL or a data.frame, the function row-binds those elements into a single data.table. It returns that table in a length-1 list, named by returned_name_when_dfs_are_not_nested.

Otherwise every element of x MUST be NULL or a fully named list. The function stops with an error if one element is not. The function names the returned list by the sorted union of the inner names. Each element is the data.table::rbindlist() of the inner elements that carry that name.

See also

vignette("csutil", package = "csutil"), which unnests a two-element list of fully named lists.

Examples

x <- list(
  list(
    "a" = data.frame("v1"=1),
    "b" = data.frame("v2"=3)
  ),
  list(
    "a" = data.frame("v1"=10),
    "b" = data.frame("v2"=30),
    "d" = data.frame("v3"=50)
  ),
  list(
    "a" = NULL
  ),
  NULL
)
print(x)
#> [[1]]
#> [[1]]$a
#>   v1
#> 1  1
#> 
#> [[1]]$b
#>   v2
#> 1  3
#> 
#> 
#> [[2]]
#> [[2]]$a
#>   v1
#> 1 10
#> 
#> [[2]]$b
#>   v2
#> 1 30
#> 
#> [[2]]$d
#>   v3
#> 1 50
#> 
#> 
#> [[3]]
#> [[3]]$a
#> NULL
#> 
#> 
#> [[4]]
#> NULL
#> 
csutil::unnest_dfs_within_list_of_fully_named_lists(x)
#> $a
#>       v1
#>    <num>
#> 1:     1
#> 2:    10
#> 
#> $b
#>       v2
#>    <num>
#> 1:     3
#> 2:    30
#> 
#> $d
#>       v3
#>    <num>
#> 1:    50
#> 

x <- list(
  data.frame("v1"=1),
  data.frame("v3"=50)
)
print(x)
#> [[1]]
#>   v1
#> 1  1
#> 
#> [[2]]
#>   v3
#> 1 50
#> 
csutil::unnest_dfs_within_list_of_fully_named_lists(
  x,
  returned_name_when_dfs_are_not_nested = "NAME",
  fill = TRUE
)
#> $NAME
#>       v1    v3
#>    <num> <num>
#> 1:     1    NA
#> 2:    NA    50
#>