How do I make my variables save from my function?

I have written a function function [f, grad, gradTwo] = Rosen(x), which returns the Rosenbrock function value f(x) to f, its gradient vector ∇f(x) to grad, and its Hessian matrix ∇f(x) to gradTwo, at the given input point x and verify the function returns correct values.

I have written a function that does so, using x = [1, 1], but my values don't store.

function [f, grad, gradTwo] = Rosen(x)
    g = @(x)100*(x(2) - x(1)^2)^2 + (1 - x(1))^2;
    f = g(x);
    grad = [-400*(x(2)-x(1)^2)*x(1)-2*(1-x(1)); 200*(x(2)-x(1)^2)];
    gradTwo = [800*x(1)+2, -400*x(1); -400*x(2), 200];
end

Then my output when I run this is:

ans =

0

I believe my professor wants it to look like this:

f =

0

grad =

0

0

gradTwo =

802 -400

-400 200

Is there a way to accomplish this? Any advice would be great, I'm not that great at MATLAB

[Sabin Thapa]

Hi, if grad = ∇f(x) and gradTwo = ∇^2 f(x), then these should be:

grad = [400*x(1)^3 - 400*x(1)*x(2) + 2*x(1) - 2; 200*(x(2)-x(1)^2)];

and gradTwo = [1200*x(1)^2 - 400*x(2) + 2, -400*x(1); -400*x(1), 200];

(related to mathematics, not coding)

Answer 1

[Hiro Yoshino]

You're doing well!

Try this:

x = [1 1]; 
[f, grad, gradTwo] = Rosen(x)

You should prepare the three variables that recieve the calculus!

[Sarah Johnson]

Thank you so much!!