Construct an N-dimensional seed backend for delarr

Creates a seed for arrays with 2 or more dimensions. The pull function receives a list of per-dimension index vectors and returns the corresponding sub-array.

Usage

delarr_seed_nd(
  dims,
  pull,
  chunk_hint = NULL,
  dimnames = NULL,
  begin = NULL,
  end = NULL
)

Arguments

dims: Integer vector of dimension extents (length >= 2).
pull: A function accepting a single argument indices — a named or positional list of integer vectors (one per dimension, or NULL for "all") — and returning an array with the requested sub-dimensions.
chunk_hint: Optional list describing preferred chunk sizes.
dimnames: Optional list of dimnames (one element per dimension).
begin: Optional function invoked before streaming begins.
end: Optional function invoked after streaming completes.

Value

An object of class delarr_seed.

Examples

arr <- array(seq_len(24), dim = c(3, 4, 2))
seed <- delarr_seed_nd(
  dims = c(3, 4, 2),
  pull = function(indices) {
    idx <- lapply(seq_along(dim(arr)), function(k) indices[[k]] %||% seq_len(dim(arr)[k]))
    do.call("[", c(list(arr), idx, list(drop = FALSE)))
  }
)
dim(seed)
#> [1] 3 4 2