# Nonlinear optimization not working

4 views (last 30 days)
userpv on 7 Oct 2022
Commented: userpv on 7 Oct 2022
Hi, I'm trying to solve the below:
min 25x+37y+48z
s.t.
z−0.25x∧2+0.1y∧2+0.01xy>=10,000
x,y,z>=200
y>=2z
So far, I have a function file:
function [c,ceq] = myfunction(x)
c(1) = z - 0.25*(x)^2 + 0.1*(y^2) + 0.01*x*y - 10000;
c(2) = x^2 - 200;
c(3) = y^2 - 200;
c(4) = z^2 - 200;
c(5) = y - 2*z;
ceq = [];
end
In the main file I have:
clc
clear
x=0;
y=0;
z=0;
fun = 25*x + 37*y + 48*z;
nonlcon=@myfunction;
x0 = [0,0,0];
A = []; % No other constraints
b = [];
Aeq = [];
beq = [];
lb = [];
ub = [];
fvalue = fmincon(fun,x0,A,b,Aeq,beq,lb,ub,nonlcon)
I'm getting the below errors:
Error using optimfcnchk
FUN must be a function, a valid character vector expression, or an inline
function object.
Error in fmincon (line 430)
Error in HW6_4 (line 15)
fvalue = fmincon(fun,x0,A,b,Aeq,beq,lb,ub,nonlcon)
Can anyone advise on how to resolve this?

Torsten on 7 Oct 2022
Edited: Torsten on 7 Oct 2022
fun = @(x,y,z) 25*x + 37*y + 48*z;
x0 = [0,0,0];
A = [0 -1 2];
b = [0];
Aeq = [];
beq = [];
lb = [200 200 200];
ub = [Inf Inf Inf];
fvalue = fmincon(@(x)fun(x(1),x(2),x(3)),x0,A,b,Aeq,beq,lb,ub,@(x)myfunction(x(1),x(2),x(3)))
Local minimum found that satisfies the constraints. Optimization completed because the objective function is non-decreasing in feasible directions, to within the value of the optimality tolerance, and constraints are satisfied to within the value of the constraint tolerance.
fvalue = 1×3
200.0000 435.0843 200.0000
function [c,ceq] = myfunction(x,y,z)
c(1) =-( z - 0.25*x^2 + 0.1*y^2 + 0.01*x*y - 10000);
ceq = [];
end
userpv on 7 Oct 2022
This fixed the issue. Thanks!

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