Optimization problem: matlab inbuilt function "getIpOptions" generates an error in fmincon

This code is used to generated the minimum quantities of two good given a cost constraints. it is a simple optimization problem using "fmincon", however when i run the code i get this problem

%{ 

Unrecognized function or variable 'getIpOptions'.

Error in fmincon (line 822)
    options = getIpOptions(options,sizes.nVar,mEq,flags.constr,defaultopt,10,0.01);

Error in langrangian (line 5)
[x,fval] = fmincon(@volume,[1 1],[],[],[],[],[0 0],[],@mycons);

%}

clear ;
clc;
close all;

[x,fval] = fmincon(@utility,[1 1],[],[],[],[],[0 0],[], @mycons);

% the utility function to be maximimzed
function u = utility(x)
    u = x(1)^(1/3)*x(2)^(2/3);
end

% subject to the cost function below
function s = cost(x)
    s = 10*x(1) + 4*x(2);
end

function[c,ceq] = mycons(x)
    c = cost(x) - 100 ; % the cost function is less than 100 (equality constraint)
    ceq = [] ; % we dont have non-linear equality constraints
end

Answer 1

[Alan Weiss]

You are trying to maximize utility, so you should minimize the negative of the utility. The following code runs without error for me:

[x,fval] = fmincon(@utility,[1 1],[],[],[],[],[0 0],[], @mycons)

% the utility function to be maximimzed

function u = utility(x)
    u = x(1)^(1/3)*x(2)^(2/3);
    u = -u;
end

% subject to the cost function below
function s = cost(x)
    s = 10*x(1) + 4*x(2);
end

function[c,ceq] = mycons(x)
    c = cost(x) - 100 ; % the cost function is less than 100 (equality constraint)
    ceq = [] ; % we dont have non-linear equality constraints
end

Alan Weiss

MATLAB mathematical toolbox documentation

[suleiman abdullahi]

Thanks for effort, however, i still get this error even after copy-pasting your code:

% { 
Unrecognized function or variable 'getIpOptions'.
Error in fmincon (line 822)
    options = getIpOptions (options, sizes.nVar, mEq, flags.constr, defaultopt, 10,0.01);
Error in langrangian (line 5)
[x, fval] = fmincon (@volume, [1 1], [], [], [], [], [0 0], [], @ mycons);

%}

[Alan Weiss]

You might need to reinstall MATLAB®. Or at least Optimization Toolbox™.

Alan Weiss

MATLAB mathematical toolbox documentation

[suleiman abdullahi]

dank, i had to install optimization add-on!