Problem adding delay to dde23 model

I have tried to add a parameter to dde23 example, but i keep getting error. What is wrong in my approach?

lags = [1 0.2];

a=5;

tspan = [0 5];
sol = dde23(@ddefun, lags, @history, tspan);

plot(sol.x,sol.y(1,:),'-o')
xlabel('Time t');
ylabel('Solution y');

function dydt = ddefun(t,y,a,Z) % equation being solved
  ylag1 = Z(:,1);
  ylag2 = Z(:,2);

  dydt = [a*ylag1(1); 
          ylag1(1)+ylag2(2); 
          y(2)];
end
%-------------------------------------------
function s = history(t) % history function for t <= 0
  s = 10*ones(3,1);
end
%-------------------------------------------

Copyright 2018 The MathWorks, Inc.

[Torsten]

Please write down the delay ODE you are trying to solve as plain text so that we can compare to your code.

[Marom Yossef]

It's the example in , and it works online but somehow here I can't run it:

DDE with Constant Delays - MATLAB & Simulink (mathworks.com)

lags = [1 0.2];

tspan = [0 5];
sol = dde23(@ddefun, lags, @history, tspan);

plot(sol.x,sol.y,'-o')
xlabel('Time t');
ylabel('Solution y');
legend('y_1','y_2','y_3','Location','NorthWest');

function dydt = ddefun(t,y,Z) % equation being solved
  ylag1 = Z(:,1);
  ylag2 = Z(:,2);

  dydt = [ylag1(1); 
          ylag1(1)+ylag2(2); 
          y(2)];
end
%-------------------------------------------
function s = history(t) % history function for t <= 0
  s = ones(3,1);
end
%-------------------------------------------

[Torsten]

What error message do you get ?

[Marom Yossef]

Unrecognized function or variable 'a'. Even when I add this parameter as an argument.

Thank you for trying to help

Answer 1

[Torsten]

lags = [1 0.2];
a = 5;
tspan = [0 5];
sol = dde23(@(t,y,Z)ddefun(t,y,Z,a), lags, @history, tspan);
plot(sol.x,sol.y(1,:),'-o')
xlabel('Time t');
ylabel('Solution y');
%-------------------------------------------

function dydt = ddefun(t,y,Z,a) % equation being solved
  ylag1 = Z(:,1);
  ylag2 = Z(:,2);
  dydt = [a*ylag1(1); 
          ylag1(1)+ylag2(2); 
          y(2)];
end
%-------------------------------------------

function s = history(t) % history function for t <= 0
  s = 10*ones(3,1);
end
%-------------------------------------------

[Marom Yossef]

Thank you so much!!