Unable to use indexed input in a user-defined function in Simulink

I have developed a function by using SImulink user-defined function. The function uses a for loop to perform math operations on previous time step (in fact a state space model). Similar to x(i) = A * x(i-1). The code works perfectly fine on mfile if I generate the test signal in mfile. Since, I want to convert the function to C code, I want to test my code in Simulink.

Simulink input is not taking indexed input to use it in for loop. An example .mdl file is attached. Where, the input of the function is used in a for loop to give output (also indexed output).