How to change output of function?

Hello,

My problem is that when my if-statement is not fullfiled and the code executes the else-statement I just want it to return the text message. But i have to assign some value to W and if i do so and call the function it also shows me that A is empty. Is it possible to chang this that it just shows me the error message without the empty Value of A?

function W = hat(w)
 sz = size(w);
    if sz == [3 1]
        W = [0 -w(3) w(2); w(3) 0 -w(1); -w(2) w(1) 0];
    else
       disp('Variable w has to be a 3-component vector!');
       W=[];
    end
end
a = [1;2];
A = hat(a)

Answer 1

[Monica Roberts]

You can use return to exit the function, but depending on how you use this function, it's usually helpful to have a default value for the output. You could also use MATLAB's built-in warning function:

function W = hat(w)
 sz = size(w);
    if sz == [3 1]
        W = [0 -w(3) w(2); w(3) 0 -w(1); -w(2) w(1) 0];
    else
       warning('Variable w has to be a 3-component vector!');
       return
    end
end

[Antonio Sarusic]

unfortunately when i tun the code i that you provided i still get the error "Output argument "W" (and possibly others) not assigned a value in the execution with "hat" function."

[Monica Roberts]

function W = hat(w)
 sz = size(w);
    if sz == [3 1]
        W = [0 -w(3) w(2); w(3) 0 -w(1); -w(2) w(1) 0];
    else
       warning('Variable w has to be a 3-component vector!');
       W = [];
       return
    end
end

Then I call the function:

>> W = hat(1)
Warning: Variable w has to be a 3-component vector! 
> In hat (line 6) 

W =

     []

[Jan]

This is fragile:

sz = size(w);
if sz == [3 1]    

== is the elementwise comparison. If the input w has more then 2 dimension, the comparison fails. Prefer the safer:

sz = size(w);
if isequal(sz, [3 1])

Or:

if isrow(w) && numel(w) == 3

[Monica Roberts]

Very true, though unrelated to the original question. I'd probably also suggest a more specific warning 'Input variable must be a 3 x 1 vector'.