Putting constraints for different parts of a matrix using fmincon

Hi everyone,

So I'm basically using fsolve, and everything's fine with it except that I'm trying to establish limits on a particular segment of the matrix 'x' that fsolve is trying to solve for.

So I put:

lb = -Inf*ones(size(x));
lb(20:22,:) = 0;
x = fmincon(fx,x0,[],[],[],[],lb,[]);

Error returned is:

Error using fmincon (line 713)
User supplied objective function must return a scalar value.

Error in runme (line 25)
x = fmincon(fx,x0,[],[],[],[],lb,[]);

Does anyone know of a way out of this problem? Thanks for the help!

[Matt J]

So I'm basically using fsolve, and everything's fine with it except that I'm trying to establish limits on a particular segment of the matrix 'x' that fsolve is trying to solve for.

I think you mean fmincon, not fsolve. That's what your example code shows and that it is a more appropriate tool for problems with bounds.

Error returned is: ... Does anyone know of a way out of this problem? Thanks for the help!

The code you've posted doesn't reveal the root cause of the problem, only that it lies inside fx(). The error message simply means that fx() is not returning a scalar value, as it is expected to.

[Walter Roberson]

Is your fx a function handle? It is common for people to forget to pass a function handle,

x = fmincon(@fx,x0,[],[],[],[],lb,[]);