rapply to nested list of data frames in R

Question

i have a nested list whose fundamental element is data frames, and i want to traverse this list recursively to do some computation of each data frame, finally to get a neste

Answer 1

Handling list computation at a specific depth:

recursive_lapply <- function (data, fun, depth = 1L) {
  stopifnot(inherits(data, "list"))
  stopifnot(depth >= 1)
  f <- function(data, fun, where = integer()) {
    if (length(where) == depth) {
      fun(data)
    } else {
      res <- lapply(seq_along(data), function(i) {f(data[[i]], fun, where = c(where, i))})
      names(res) <- names(data)
      res
    }
  }
  f(data, fun)
}

example computation:

d <- list(
  A = list(a = list(
    a1 = data.table::data.table(x = 11:15, y = 10:14),
    a2 = data.table::data.table(x = 1:5, y = 0:4)
  )),
  B = list(b = list(
    b1 = data.table::data.table(x = 7, y = 8),
    b2 = data.table::data.table(x = 9, y = 10)
  ))
)

> recursive_lapply(d, function(data) data[, "z":= x + y], 3)
$A
$A$a
$A$a$a1
    x  y  z
1: 11 10 21
2: 12 11 23
3: 13 12 25
4: 14 13 27
5: 15 14 29

$A$a$a2
   x y z
1: 1 0 1
2: 2 1 3
3: 3 2 5
4: 4 3 7
5: 5 4 9

$B
$B$b
$B$b$b1
   x y  z
1: 7 8 15

$B$b$b2
   x  y  z
1: 9 10 19