I dont know how to fix MILP error

 function f = fit(q)
    J = 1;
    T = 2;
    K = 2;
    %item,period
    R = reshape(q(1:J*T),J,T); 
    IP = reshape(q(J*T+1:J*T*2+1),J,T);
    IM = reshape(q(J*T*2+2:J*T*3+2),J,T); 
    XS = reshape(q(J*T*3+3:J*T*4+3),J,T); 
    X = reshape(q(J*T*4+4:J*T*4+4+J*K*T),J,K,T); 
    MAB = reshape(q(J*T*4+5+J*K*T:J*T*5+5+J*K*T),K,T); %binary
    MIB = reshape(q(J*T*5+6+J*K*T:J*T*5+6+J*K*T*2),J,K,T);%binary

    i=0.1;
    a = [3; 2];
    cr = [3.5; 1.5];
    c = [3.5 1.5];
    h = 3.5;
    b = 1;
    A = [2 3];
for j = 1:J
    for k = 1:K
        for t = 1:T
            H(j,t) = (1/(1+i)^t)*((h(j)*(R(j,t)+IP(j,t))/2)+b(j)*IM(j,t)+c(j,t)*XS(j,t));
            MAO(k,t) = (1/(1+i)^t)*(A(k)*MAB(k,t));
            MIO(j,k,t) = (1/(1+i)^t)*(a(j,k)*MIB(j,k,t)+cr(j,k)*X(j,k,t));
        end
    end
end
      f = H + MaO + MiO;
      intcon = 1:J*T*5+6+J*K*T*2;
      lb = zeros(J*T*5+6+J*K*T*2,1);
      ub = ones(1:J*T*5+6+J*K*T*2,1);
      ub(1:J*T*4+4+J*K*T)=inf;

 x = intlinprog(@fit,intcon,lb,ub);

I made this code. I try to solve this use intlinprog. but error message tells me "Not enough input arguments."

How can I fix it? Am i using intlinprog as a wrong way?

Answer 1

[Ced]

I'm afraid so, yes. Two main points:

1. The function to minimize has to be linear one (hence the name linear program) and has to be passed as a numerical vector. Meaning: You need to reformulate your problem as fit(q) = f'*q, and then pass f to intlinprog.

2. The correct order of arguments is

X = intlinprog(f,intcon,A,b,Aeq,beq,LB,UB)

If your problem does not have certain parts, e.g. the equality constraints, then you need to pass empty matrices [] instead. You can't just leave them away.

I put together a little dummy example to show you how this works:

function x_sol = my_int_minimizer()

% simple example:
% min( -x1 -x2 + x3) 
% s.t. 
% (1.) x1 + x2 + x3 <= 5.5
% (2.) x2 <= 2
% (3.) x3 >= 1
% (4.) x1 integer

% vector of unknowns: x, dimension 3x1

% function to minimize: J = f'*x
f = [ -1 -1 1 ]';

% integer constraint (4.)
intcon = 1;

% inequality constraint A*x <= b (1.)
Aineq = [ 1 1 1 ];
bineq = 5.5;

% equality constraints (none)
Aeq = [];
beq = [];

% lower / upper bounds
lb = [ -inf -inf 1 ]'; % (3.)
ub = [ inf 2 inf ]';   % (2.)

% solve problem
x_sol = intlinprog(f,intcon,Aineq,bineq,Aeq,beq,lb,ub);

% output solution
disp(x_sol)

end

Cheers

[Matlab Noob]

I don't know why this code is not running on my matlab...

[Alan Weiss]

Did you read what Ced told you? Your objective function cannot be nonlinear, it must be a simple vector of constants. See the intlinprog function reference page for the f argument (the objective).

Alan Weiss

MATLAB mathematical toolbox documentation