`empty`

Creates an empty array of a given class.

Syntax

E = ClassName.empty

Returns a 0-by-0 empty array of the class.

E = ClassName.empty(m, n, ...)

Returns an empty array with the given size, in which at least one dimension is 0.

Description

empty makes it explicit what type of data an empty variable will hold, and gives it a specific shape. That shape matters: a 0-by-3 empty matrix is the right starting point for building a table of three-column rows with vertical concatenation, while [] is 0-by-0.

It also creates empty arrays of objects, as in MyClass.empty, which can later grow by indexing.

Input arguments

ClassName: A class name such as double, char, single, int8, cell or struct, or a user-defined class.
m, n, ...: Dimension sizes. At least one must be 0, otherwise it is an error.

Output arguments

E: Empty array of the requested class and size.

Example

Typed empty arrays

x = double.empty(0, 3);
size(x)
rows = [x; 1 2 3; 4 5 6]
class(int8.empty(2, 0))
size(cell.empty)

Output

ans = 1×2

     0     3
rows = 2×3

     1     2     3
     4     5     6
ans = 'int8'
ans = 1×2

     0     0

Notes

empty works for the built-in classes. For a user-defined class, MyClass.empty is not yet recognized.

empty