Re: Multiple outputs from fmincon

Steve, it is possible that a solution is to remove a semicolon:

function x = try1(q)
x = -(4*q-.5*q^2);
y = -(5*q-23)*x % note: no semicolon


Here's a transcript of the MATLAB run:

[q,fval]=fmincon(@try1,x0,A,b);
Warning: Trust-region-reflective algorithm does not currently solve this type of problem,
using active-set (line search) instead.
> In fmincon at 436

y =

0


y =

-1.3709e-006


y =

-24.0000


y =

-24.0000


Local minimum found that satisfies the constraints.

Optimization completed because the objective function is non-decreasing in
feasible directions, to within the default value of the function tolerance,
and constraints were satisfied to within the default value of the constraint tolerance.

Alan Weiss
MATLAB mathematical toolbox documentation

Steve Kasperski wrote:
I am having trouble getting multiple outputs from fmincon. I want to retrieve the solution, the value of the objective function, and a third output which is a function of both the optimal solution as well as the value of the objective function. The simpliest form of this problem I could think of is described below:

function [x,y] = try1(q)
x=-(4*q-.5*q^2);
y=-(5*q-23)*x;

x0=0;
A=1;
b=10;
[q,fval]=fmincon(@try1,x0,A,b);

The solution to this problem is obvious (q=4;x=-8;y=-24), but the only outputs I can get from fmincon are q=4 and fval=x=-8. My real problem is too complicated to discuss here, but y is not something that can be calculated after the values of q and x are determined by fmincon. Therefore I need fmincon to display multiple outputs or have an output function that displays the value of q, x, and y at every iteration and I can just take the ending value for y.

Any suggestions are welcome. Thanks for reading.

Steve
.

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