MATLAB: How to obtain a fixed-size array from a variable-size array

fixed size arrayvariable size array

I'm using the Matlab Function block in Simulink and I have the following problem :
In my code, I have a two vectors : 'A0', of fixed-size and 'A1', of variable-size.
The size of 'A0' is 'n0', thus A0(n0,1) The maximum size of A1 is 'n0'. Thus, (Size of A1) <= (Size of A0).
One of the outputs of my Matlab Function is A = A0 + A1. Since it's a sum of vectors, they must have the same size, so what I did is fill 'A1' with zeros until reaching the same size. For exemple :
n0 = length(A0);
n1 = length(A1) ;
m = n0 - n1 ;
if n1 < n0 
    A1_1 = [A1 ; zeros(m,1)] ;
else
    A1_1 = A1 ;
end
A = A0 + A1_1 ;
I believe that with this code, 'A', 'A1_1' and 'A0' will always have the same fixed size (since the reference, 'A0', is already fixed). In my simulation, I get the value of 'A' that I desire.
The problem is that for Simulink, 'A' is still a variable-size array, so I can't branch its signal directly with some other blocks.
What I need is 'A' (or even 'A1_1') to be read by Matlab-Simulink as a fixed-size array.

Best Answer

Because you are doing dynamic allocation,
A1_1 = [A1 ; zeros(m,1)] ;
MATLAB has no way of knowing what will be the final size of A1_1. To avoid such problem, try initializing A1_1 and other variables with a fixed maximum size
A1_1 = zeros(size(A0)); % or maximum size.
and then assign values to A1_1 using indexing. This way MATLAB will know in advance that what is the maximum size that these variables can take and thus consider then as fixed size array.
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