How can I measure length of signal in simulink?

Hello guys, I have model with "matlab function block" in which I have recursive least square method. Recursive algorithm needs to know length of incoming signal in order to work correctly. But when I use command N=length(y) it returns me length N= 1. But I think it should give me higher length.

 Matlab function block code "rls_iden6"

function [P,N] = fcn(u,y)
N = length(y);
sigma=1;       
C = sigma*eye(2);      %p
P = ones(2,1);

z= [y; u];
lamda=1;
for n=1:N
sample_out = y(n);
C = (C - ( (C*z*z'*C)/( lamda+(z'*C*z) ) ))/lamda;
P = P + (C*z* (sample_out - (z'*P)));  
end

My final code should look like it's shown below, because it works in matlab workspace. Simulink should give me 5 parameters instead of just 2.

load data_cela.mat
u=U; %input
y=Y; %output
input = 3;
output = 2;
system = input + output;   
N = length(y);              
%initial conditions
sigma = 1;        
C = sigma*eye(system);      
P = ones(system,1);        
lamda = 1;               %forgetting factor

for n=3:N
    for i=1:2
        W(i) = y(n-i);          %output
    end
    for i=1:3
        V(i) = u(n-i+1);        %input
    end
    z = [V';W'];
    sample_out = y(n);
    pom(n)= z' * P;
    error(n) = y(n) - pom(n); 
    C = (C - ( (C*z*z'*C)/( lamda+(z'*C*z) ) ))/lamda;

      P = P + (C*z* (sample_out - (z'*P) ) );
      change(1:system,n) = P;
  end
  f_param = [P(1:3);-P(4:5)];
  num = [P(1:3,1)];
  den = [1;-P(4:5,1)];
  num1 = num(3,1);
  trasferfunction = tf(num1,den',1)

Result:

           0.002879
    ----------------------
    z^2 - 1.883 z + 0.8873

[Jim Riggs]

Verify the signal size in Simulink. In the Simulink window, select Display / Signals & Ports / Signal Dimensions.

This will show the signal size (according to Simulink) in your model.