问题
I'm trying to optimize a function with 2 inputs. Trying to use fminsearch but it keeps saying undefined function or variable although it is already defined.
I have already defined the function in a separate script that is in the same directory with my main script. I have a classroom license which includes optimization toolbox and there is no spelling mistake while calling the function.
function o=u(x,y)
%some code here
end
%in a second script
init=[0.1,0.1];
b=fminsearch(o,init);
The error is:
Undefined function or variable 'o'.
回答1:
From the documentation on fminsearch, the function being minimized must have a single argument and accessed with a function handle (see this related answer).
The error you are getting is because you can't call o and use it as an input to fminsearch() since o is undefined. To get o, you have to first get u(x,y), plus as mentioned, fminsearch requires a function handle as an input.
You have several options that still use your standalone function, u(x,y).
1. Create a function handle
Define a function handle that calls u(x,y) but has a single argument which is a 2 x 1 vector, z = [x; y].
fh =@(z) u(z(1),z(2));
z0 = [1; 2]; % Initial Guess for z = [x; y]
[z,TC] = fminsearch(fh,z0)
2. Change the function and call it directly
The same result is possible with
[z,TC] = fminsearch(@u,z0)
if you redefine u(x,y) to be as follows:
function o=u(z)
x = z(1);
y = z(2);
% your function code here
end
来源：https://stackoverflow.com/questions/57059519/why-do-i-get-fminsearch-undefined-function-error