Size mismatch error using Matlab function to solve equations

Hi All,

Im trying to use matlab function in simulink using the following code:

1. function S= fcn (A,B,C,D,E)
2. R=roots([A B C D E]); %ABCDE are coefficients of a polynomial that i want to solve and are preovided as real constants
3. k=(zeros(1,4));
4. k=R(imag®==0);% to discard the complex roots. this is my requirement
5. k=real(k);
6. S=zeros(1,4);
7. S(:)=k;

The size of S is specified as [1,4] in the model explorer. I have to use fixed size calculations. When I run this code, I get a runtime error, "simulation stopped due to size mismatch error 4~=0." When I stop the debugger, the function block gets highlighted and I get the following error,: MATLAB Function Interface Error: Unknown MATLAB error encountered. Block Equation (#1512) While executing: none

Can somebody help me plese? Thanks in advance

Answer 1

[Andrei Bobrov]

R=roots([A B C D E]);
S=zeros(1,4);
t = abs(imag(R)) < eps(100);
S(t)=real(R(t));