How do I make my variables save from my function?
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Sarah Johnson
le 19 Fév 2020
Modifié(e) : Sabin Thapa
le 17 Fév 2021
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.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/272495/image.png)
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
1 commentaire
Sabin Thapa
le 17 Fév 2021
Modifié(e) : Sabin Thapa
le 17 Fév 2021
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)
Réponse acceptée
Hiro Yoshino
le 19 Fév 2020
You're doing well!
Try this:
x = [1 1];
[f, grad, gradTwo] = Rosen(x)
You should prepare the three variables that recieve the calculus!
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