Real root filtering using Embedded matlab function

Hello,

I have used an embedded matlab function in simulink to select the real root from previous block. Following is the code that I have written in this block: function y = clipping (u) coder.varsize('y',[1 4]); thresh = 10*eps; y= real(u(~isnan(u) & abs(imag(u)) < thresh));

the essential point is y should be vary from 2 roots to 4

but I have the following Error: Output 'y' (#231) has variable size but the upper bound is not specified; explicit upper bound must be provided.

Best Regards, Amro