want to see where is the problem in this code doesn't give me result

function J = system_model_jacobian(x,y,z,k,a1,a2,b2,c,d,p,sigma,beta)
J = [p*(1-x/k)-a1*y, -a1*x+c*a1*y/(b2+y)-d, 0;        a2*y*z/(b2+y)^2, c*a1*x*z/(b2+y)^2-d, -beta*z^2/(b2+y)+2*sigma*z;        0, 0, 0];

% Compute Jacobian matrix at the steady states
x1 = [0, 0, 0];
x2 = [k, 0, 0];
x3 = [d/(c*a1), p*b1/(c*k*a1^2), 0];
x4 = [(k*(sigma*p-a1*b2))/(p*sigma), p*b1/(c*k*a1^2), beta*(p*sigma*b1-c*a1^2*b2)/(a2*p*sigma^2)];

J1 = subs(J,{x,y,z},{x1(1),x1(2),x1(3)});
J2 = subs(J,{x,y,z},{x2(1),x2(2),x2(3)});
J3 = subs(J,{x,y,z},{x3(1),x3(2),x3(3)});
J4 = subs(J,{x,y,z},{x4(1),x4(2),x4(3)});

% Compute eigenvalues of each steady state
lambda1 = eig(J1);
lambda2 = eig(J2);
lambda3 = eig(J3);
lambda4 = eig(J4);

% Display results
disp('Steady State 1:');
disp(['Eigenvalues: ', num2str(lambda1(1)), ', ', num2str(lambda1(2)), ', ', num2str(lambda1(3))]);
disp('Steady State 2:');
disp(['Eigenvalues: ', num2str(lambda2(1)), ', ', num2str(lambda2(2)), ', ', num2str(lambda2(3))]);
disp('Steady State 3:');
disp(['Eigenvalues: ', num2str(lambda3(1)), ', ', num2str(lambda3(2)), ', ', num2str(lambda3(3))]);
disp('Steady State 4:');
disp(['Eigenvalues: ', num2str(lambda4(1)), ', ', num2str(lambda4(2)), ', ', num2str(lambda4(3))]);
end

[the cyclist]

Give us an example of inputs that you call the function with.

When you say, "doesn't give me a result", what do you mean? Does it give an error? Does it not output J? Does it not display the eigenvalues?

[Steven Lord]

What does "doesn't give me result" mean in this context?

• Do you receive warning and/or error messages? If so the full and exact text of those messages (all the text displayed in orange and/or red in the Command Window) may be useful in determining what's going on and how to avoid the warning and/or error.
• Does it do something different than what you expected? If so, what did it do and what did you expect it to do?
• Did MATLAB crash? If so please send the crash log file (with a description of what you were running or doing in MATLAB when the crash occured) to Technical Support so we can investigate.

[Rik]

This is perhaps related to the previous question, but that context might not be that helpful.

Answer 1

[Image Analyst]

What did you pass in for x,y,z,k,a1,a2,b2,c,d,p,sigma,beta? You didn't just click the green run triangle, did you? Because doing that will not "invent" values to pass in for you.

What do you mean by "give me result"? Did you mean it doesn't give you any result at all? Or did you mean it gave you a result, but not the result you expected?

[Ahmad]

i mean doesn't give me reslts, i mean output.

[Image Analyst]

@Ahmad I think you overlooked my first paragraph so I need to repeat it:

What did you pass in for x,y,z,k,a1,a2,b2,c,d,p,sigma,beta? You didn't just click the green run triangle, did you? Because doing that will not "invent" values to pass in for you.

I'll check back later for your reply.

[Ahmad]

yes i did

[Image Analyst]

Well then, that's your problem. You can't just click the green run triangle because it won't know the values of the input arguments. For example, should it think x is 4, or should it think x is 1000? How could it possibly know? What if you thought x was 300 and it just invented a value of 4000 for x? That wouldn't be right. Why aren't you assigning the values of those input variables like you need to?

[Ahmad]

so what i have to do exactly ?

[Image Analyst]

You have to assign them to something, so your test script would be something like this

x = 1
y = 2
z = 3
k=42
a1=9
a2=5
b2=6
c=99
d=234234
p=4234
sigma=234
beta=0.5
J = system_model_jacobian(x,y,z,k,a1,a2,b2,c,d,p,sigma,beta)