Description

extract_array is an internal generic function not aimed to be used directly by the user. It has methods defined for array, data.frame, DataFrame objects and other array-like objects.

The DelayedArray() constructor function will accept any seed that complies with the seed contract i.e. that supports dim(), dimnames(), and extract_array().

Usage

Arguments

Details

extract_array methods need to support empty and missing subscripts e.g. extract_array(x, list(NULL, integer(0))) must return an M x 0 matrix and extract_array(x, list(integer(0), integer(0))) a 0 x 0 matrix.

Also subscripts are allowed to contain duplicated indices so things like extract_array(seed, list(c(1:3, 3:1), 2L)) need to be supported.

type(x) returns the type of the elements in x. It's equivalent to typeof(x) or storage.mode(x) on an ordinary array or vector. It works out-of-the-box on any array-like object x for which extract_array(x) works.

Value

extract_array must return an ordinary array of the appropriate type (i.e. integer, double, etc...). For example, if x is an object representing an M x N matrix of complex numbers, extract_array(x, list(NULL, 2L)) must return its 2nd column as an ordinary M x 1 matrix of type complex.

type returns the type of the array elements.

See Also

• read_block.

• array and data.frame objects in base R.

• DataFrame objects in the S4Vectors package.

• DelayedArray objects.

Examples