A matrix may have one or both dimensions zero, and operations on empty
matrices are handled as described by Carl de Boor in An Empty
Exercise, SIGNUM, Volume 25, pages 2-6, 1990 and C. N. Nett and W. M.
Haddad, in A System-Theoretic Appropriate Realization of the Empty
Matrix Concept, IEEE Transactions on Automatic Control, Volume 38,
Number 5, May 1993.
Briefly, given a scalar `s`, an `m` by
`n` matrix `M(mxn)`

, and an `m` by `n` empty matrix
`[](mxn)`

(with either one or both dimensions equal to zero), the
following are true:

s * [](mxn) = [](mxn) * s = [](mxn) [](mxn) + [](mxn) = [](mxn) [](0xm) * M(mxn) = [](0xn) M(mxn) * [](nx0) = [](mx0) [](mx0) * [](0xn) = 0(mxn)

By default, dimensions of the empty matrix are printed along with the
empty matrix symbol, ‘`[]`’. The built-in variable
`print_empty_dimensions`

controls this behavior.

- Built-in Function:
`val`=**print_empty_dimensions***()* - Built-in Function:
`old_val`=**print_empty_dimensions***(*`new_val`) - Built-in Function:
**print_empty_dimensions***(*`new_val`, "local") Query or set the internal variable that controls whether the dimensions of empty matrices are printed along with the empty matrix symbol, ‘

`[]`’. For example, the expressionzeros (3, 0)

will print

ans = [](3x0)

When called from inside a function with the

`"local"`

option, the variable is changed locally for the function and any subroutines it calls. The original variable value is restored when exiting the function.**See also:**format.

Empty matrices may also be used in assignment statements as a convenient way to delete rows or columns of matrices. See Assignment Expressions.

When Octave parses a matrix expression, it examines the elements of the list to determine whether they are all constants. If they are, it replaces the list with a single matrix constant.