CODEWITHSUNDEEP
matlab
osimer pothe
osimer pothe

Reputation: 2897

Linear Programming solvable by MATLAB

I want to solve linear Programming by MATLAB . For this purpose , I am following the following link . Linear Programming .

Here , a sample problem is given :

Find x that minimizes

f(x) = –5x1 – 4x2 –6x3,

subject to

x1 – x2 + x3 ≤ 20 3x1 + 2x2 + 4x3 ≤ 42 3x1 + 2x2 ≤ 30 0 ≤ x1, 0 ≤ x2, 0 ≤ x3.

First, enter the coefficients

f = [-5; -4; -6]; A = [1 -1 1 3 2 4 3 2 0]; b = [20; 42; 30]; lb = zeros(3,1);

Next, call a linear programming routine.

[x,fval,exitflag,output,lambda] = linprog(f,A,b,[],[],lb);

My question is that what is meant by this line ?
lb = zeros(3,1); Without this line , all problems solvable by MATLAB is seen as infeasible . Can you help me in this purpose ?

Upvotes: 0

Views: 192

Answers (1)

Bentoy13
Bentoy13

Reputation: 4956

This is not common to ALL linear problems. Here you deal with a problem where there are some constraints on the minimal values of the solution:

0 ≤ x1, 0 ≤ x2, 0 ≤ x3

You have to set up these constraints in the parameters of your problem. The way to do so is by specifying lower boundaries of the solution, which is the 5th argument.

Without this line, the domain on which you search for a solution is not bounded, and exitflag has the value -3 after calling the function, which is precisely the error code for unbounded problems.

Upvotes: 1

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