ListPermute: Permute the levels of a nested list

In EpiForsk: Code Sharing at the Department of Epidemiology Research at Statens Serum Institut

Permute the levels of a nested list

Description

ListPermute() permutes the nesting structure of a nested list. e.g. x[["a"]][["b"]][["c"]] is equivalent to ListPermute(x, c(3, 1, 2))[["c"]][["a"]][["b"]].

Usage

ListPermute(x, order, depth = NULL, enforce_rectangular = TRUE)

Arguments

x	A nested list. By default, the list is assumed to be rectangular. If enforce_rectangular = FALSE, the length of each level in the list will be based on the first element from the level above.
order	A numeric vector, containing a permutation of the levels of x. If depth is user specified, the length of order must equal depth.
depth	A natural number or NULL (default). If NULL, the depth of the list is inferred by following the first element of the list at each level until the next element is not a list. If a natural number, a number smaller than the actual depth of x will result in permutation of the lists at the level of depth, and a number higher than the actual depth of x will result in extra levels added to the output at the locations specified by order.
enforce_rectangular	logical, should the function exit with an error in case x is not rectangular?

Value

A list, with the components of x permuted according to order.

Author(s)

KIJA

Examples

list_builder <- function(len, nm = NULL, index = NULL, len_orig = len) {
  out <- vector("list", len[1])
  if (!is.null(nm)) names(out) <- nm[[1]]
  if (length(len) > 1) {
    return(
      lapply(
        if (is.null(nm)) seq_along(out) else structure(seq_along(out), names = nm[[1]]),
        \(i) {
          list_builder(
          len = len[-1],
          nm = if (is.null(nm)) NULL else nm[-1],
          index = c(index, i),
          len_orig = len_orig
          )
        }
      )
    )
  } else {
    for (i in seq_along(out)) {
      index2 <- c(index, i)
      out[[i]] <- as.numeric(
      (index2 - c(rep(1, length(len_orig) - 1), 0)) %*%
      c(rev(cumprod(rev(len_orig[-1]))), 1)
      )

    }
    return(out)
  }
}

l1 <- list_builder(c(3, 2))
ListPermute(l1, c(2,1))

l2 <- list_builder(c(3, 2), list(letters[24:26], letters[14:13]))
ListPermute(l2, c(2,1))

l3 <- list_builder(
c(4, 3, 2),
list(letters[1:4], letters[24:26], letters[14:13])
)
ListPermute(l3, c(2,1,3))

l4 <- list_builder(
c(4, 3, 2, 3),
list(letters[1:4], letters[24:26], letters[14:13], letters[16:18])
)
ListPermute(l4, c(4, 1, 2, 3))

l5 <- list_builder(
c(4, 3, 2, 3), list(letters[1:4], letters[24:26], letters[14:13], letters[16:18])
)
l5a <- l5
for (i in 3:4) {
  for (j in 1:3) {
    for (k in 1:2) {
      l5a[[i]][[j]][[k]] <- l5[[i]][[j]][[k]][[1]]
    }
  }
}
l5b <- l5
for (i in 1:2) {
  for (j in 1:3) {
    for (k in 1:2) {
      l5b[[i]][[j]][[k]] <- l5[[i]][[j]][[k]][[1]]
    }
  }
}
ListPermute(l5, c(3, 1, 2), depth = 3L)
ListPermute(l5a, c(4, 1, 2, 3), depth = 4L, enforce_rectangular = FALSE)
ListPermute(l5b, c(4, 1, 2, 3), depth = 4L, enforce_rectangular = FALSE)

l6 <- list()
ListPermute(l6, vector("numeric"))

l7 <- list(c(1, 2))
ListPermute(l7, 1)

EpiForsk documentation built on Aug. 21, 2025, 5:31 p.m.