Invert Sublists

Inverts elements in lists within a list such that those elements (at depth 3) are regrouped by position or name within each sublist (depth 2).

Usage

invert_sublists(x, use_sublist_names = FALSE)

Arguments

x

A list of non-empty lists.

use_sublist_names

Whether to use sublist names for inversion, as TRUE or FALSE (default). See 'Details' for specifics.

Details

The use_sublist_names alters how sublists are inverted as follows:

• When FALSE, sublist elements are inverted by position within sublists. Sublists must all have the same number of elements. The original sublist names will be preserved (now at depth 3) but original depth 3 names (now sublists) will be dropped.

• When TRUE, all sublists elements (depth 3) must be named and names must not be duplicated within any given sublist. Also, matching names must exist across all sublists, as names are used for inversion itself, as well as, to name inverted sublists (names from depth 3 are moved to depth 2) in output. All sublists must still have the same number of elements.

Examples

.l <- list(
    list(1, "a", TRUE),
    list(2, "b", FALSE)
)
invert_sublists(.l)
#> [[1]]
#> [[1]][[1]]
#> [1] 1
#> 
#> [[1]][[2]]
#> [1] 2
#> 
#> 
#> [[2]]
#> [[2]][[1]]
#> [1] "a"
#> 
#> [[2]][[2]]
#> [1] "b"
#> 
#> 
#> [[3]]
#> [[3]][[1]]
#> [1] TRUE
#> 
#> [[3]][[2]]
#> [1] FALSE
#> 
#> 

# sublist element ('item') names are dropped when inverting by position but
#    sublist names are retained
.l_nm <- list(
    subl1 = list(item1 = 1, item2 = "a", item3 = TRUE),
    subl2 = list(item1 = 2, item2 = "b", item3 = FALSE)
)
invert_sublists(.l_nm, use_sublist_names = FALSE)
#> [[1]]
#> [[1]]$subl1
#> [1] 1
#> 
#> [[1]]$subl2
#> [1] 2
#> 
#> 
#> [[2]]
#> [[2]]$subl1
#> [1] "a"
#> 
#> [[2]]$subl2
#> [1] "b"
#> 
#> 
#> [[3]]
#> [[3]]$subl1
#> [1] TRUE
#> 
#> [[3]]$subl2
#> [1] FALSE
#> 
#> 

# all names are retained when inverting by name
.res1 <- invert_sublists(.l_nm, use_sublist_names = TRUE)
.res1
#> $item1
#> $item1$subl1
#> [1] 1
#> 
#> $item1$subl2
#> [1] 2
#> 
#> 
#> $item2
#> $item2$subl1
#> [1] "a"
#> 
#> $item2$subl2
#> [1] "b"
#> 
#> 
#> $item3
#> $item3$subl1
#> [1] TRUE
#> 
#> $item3$subl2
#> [1] FALSE
#> 
#> 

# names are used for inverting, so order can be different
.l_nm2 <- list(
    subl1 = list(item1 = 1, item2 = "a", item3 = TRUE),
    subl2 = list(item2 = "b", item3 = FALSE, item1 = 2) # order changed
)

## invert by name -> results the same, despite order change
.res2 <- invert_sublists(.l_nm2, use_sublist_names = TRUE)
identical(.res1, .res2)
#> [1] TRUE

## invert by pos -> results differ
.res3 <- invert_sublists(.l_nm2, use_sublist_names = FALSE)
identical(.res1, .res3)
#> [1] FALSE