Tests for the existence of a variable. The general syntax for its use is
y = exist('varname')
The return is 1
if a variable with the name varname
exists in
the current workspace and is not empty. This function is primarily
useful when keywords are used in function arguments.
Some examples of the exist
function. Note that generally exist
is used in functions to test for keywords. For example,
function y = testfunc(a, b, c) if (~exist('c')) % c was not defined, so establish a default c = 13; end y = a + b + c;
An example of exist
in action.
--> a = randn(3,5,2) a = <double> - size: [3 5 2] (:,:,1) = Columns 1 to 2 -0.0361639933961680 -0.238187257168569 -0.140415140955028 0.599755385896831 0.693389551907565 0.708649351074680 Columns 3 to 4 -0.939406097470966 -0.164794584325194 -0.00648807006806828 0.0101167556598398 -0.0530953547548948 0.160105749424486 Columns 5 to 5 -1.465385481298682 -0.0395884566172688 1.182465366442761 (:,:,2) = Columns 1 to 2 -0.744595958059576 -1.029772319457510 0.647296600570314 0.691289627813676 -0.403233868578614 -0.513911033581514 Columns 3 to 4 -0.625280812142897 0.747620555277489 -0.121927486686842 -0.844868680099879 0.502771253977369 0.438758894856345 Columns 5 to 5 -0.567515585636787 0.840068850555420 -1.266240568477841 --> b = [] b = <double> - size: [] [] --> who Variable Name Type Flags Size a double [3 5 2] b double [] ans double [] --> exist('a') ans = <logical> - size: [1 1] 1 --> exist('b') ans = <logical> - size: [1 1] 0 --> exist('c') ans = <logical> - size: [1 1] 0