The command defined determines whether the variable M is defined in MATLAB®. By default, when no attribute parameter is specified, the defined command checks whether a variable named M exists in the MATLAB® environment.

If the command contains the optional parameter 'function', then defined returns a value of 'true' only if a function named $M$ is defined in the MATLAB® environment. The option 'globalvar' returns 'true' if the variable M is defined in the MATLAB® environment and it is a global variable.

To set a global variable in MATLAB®, define the variable as a global by using Matlab[setvar], with the optional parameter 'globalvar' as in the calling sequence Matlab[setvar]("M", value, 'globalvar'). Variables must be declared as global to work with functions that use global variables of the same name.

The defined command establishes whether M exists in the MATLAB® session.  Executing the defined command returns either 'true' or 'false'.

$\mathrm{with}\left(\mathrm{Matlab}\right)\:$

$\mathrm{maplematrix\_a}≔\mathrm{LinearAlgebra}\left[\mathrm{RandomMatrix}\right]\left(2\right)$

$\mathrm{Matlab}\left[\mathrm{setvar}\right]\left(''matlabmatrix\_a''\,\mathrm{maplematrix\_a}\right)$

$\mathrm{Matlab}\left[\mathrm{defined}\right]\left(''matlabmatrix\_a''\right)$

$\mathrm{Matlab}\left[\mathrm{defined}\right]\left(''maplematrix\_a''\right)$

$\mathrm{Matlab}\left[\mathrm{setvar}\right]\left(''y''\,10.123\,'\mathrm{globalvar}'\right)$

$\mathrm{Matlab}\left[\mathrm{defined}\right]\left(''y''\,'\mathrm{globalvar}'\right)$

$\mathrm{Matlab}\left[\mathrm{defined}\right]\left(''example''\,'\mathrm{function}'\right)$

$\mathrm{Matlab}\left[\mathrm{defined}\right]\left(''y''\,'\mathrm{variable}'\right)$

$\mathrm{Matlab}\left[\mathrm{evalM}\right]\left(''answer\; =\; example(2)''\right)$

$\mathrm{Matlab}\left[\mathrm{getvar}\right]\left(''answer''\right)$