Successively Applies a Function at Each Index in a List

Successively applies a function (intersect, by default) to elements at each index level in a list.

list_reduction(
  inlist,
  FUN = intersect,
  flatten = FALSE,
  sorted = FALSE,
  MoreArgs = NULL
)

Arguments

inlist	The input list.
FUN	The function to be applied. Note that the supplied function should be one that you would expect to have work with two or more vectors as the given arguments. Thus, you can expect range to work, but not mean.
flatten	Logical. Should the output be simplified from a list. Defaults to FALSE. This is useful when you expect the result at each list index to be a single value (for example, when using a function like sum or max).
sorted	Logical. Should the values at each list index be sorted? Defaults to FALSE.
MoreArgs	A list of additional arguments to be passed to FUN. See base::mapply() for more details.

Value

A list (default) or a simple vector (if flatten = TRUE).

References

See: https://stackoverflow.com/q/62454705/1270695

See also

base::Reduce(), base::mapply()

Author

Ananda Mahto

Examples

L <- list(colA = list(c("a", "b", "c", "ñ"), c("f", "g", "h"), c("i", "j", "k")), 
          colB = list(c("d", "b", "e"), c("f", "g", "m", "p"), c("f", "o", "j")),
          colC = list(c("a", "b", "g"), c("l", "g", "f", "k", "h"), c("j", "o", "l")))
list_reduction(L)
#> [[1]]
#> [1] "b"
#> 
#> [[2]]
#> [1] "f" "g"
#> 
#> [[3]]
#> [1] "j"
#> 
list_reduction(L, flatten = TRUE)
#> [1] "b"    "f, g" "j"   

set.seed(1)
L2 <- replicate(3, replicate(3, sample(sample(20), sample(10), TRUE), FALSE), FALSE)
list_reduction(L2)
#> [[1]]
#> integer(0)
#> 
#> [[2]]
#> integer(0)
#> 
#> [[3]]
#> [1] 4 5
#> 
list_reduction(L2, sum, flatten = TRUE)
#> [1] 192 184 259
list_reduction(L2, range)
#> [[1]]
#> [1]  1 19
#> 
#> [[2]]
#> [1]  1 20
#> 
#> [[3]]
#> [1]  1 19
#> 
list_reduction(L2, union)
#> [[1]]
#>  [1]  5  6  4  8  1  2  9 14  7 19  3 12 18 10 17
#> 
#> [[2]]
#>  [1] 17  4 16 12  7  3 20  1  5  6 10  2 13 14 19  9
#> 
#> [[3]]
#>  [1]  3  1  2 15 12  6  8  4 14  5  9 19 10 17 13 18  7
#> 
list_reduction(L2, union, sorted = TRUE)
#> [[1]]
#>  [1]  1  2  3  4  5  6  7  8  9 10 12 14 17 18 19
#> 
#> [[2]]
#>  [1]  1  2  3  4  5  6  7  9 10 12 13 14 16 17 19 20
#> 
#> [[3]]
#>  [1]  1  2  3  4  5  6  7  8  9 10 12 13 14 15 17 18 19
#>