cheching exist Variable on the IF statment

How to check the exist of the one variable that does not exist in if statment.

for example we have a function that need x,y variable, and we have a equation without y in it. if i run the Function it error the missing y,,,, i want to check that if it is not exist ,GIve it some value in the IF statment and then display that y is missing beside the error of the system...

[Adam Danz]

Do you mean the variable y is not defined or the variable y is missing from the function itself?

For example, is this the problem

x = 2; 
z = x+y;

or is this the problem,

x = 2; 
y = 3; 
fun = @(x)x^2; 
z = fun(x);

Better yet, provide a working example of what you're doing.

Answer 1

[DGM]

Something like this

if ~exist('myvariable','var')
    % set default value or error or whatever
end

Although using exist() during input handling is typically slower than methods using varargin