# Add a constraint to Ax>b using intlinprog

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Ismaeel il 16 Gen 2017
Commentato: Ismaeel il 17 Gen 2017
I have a matrix A with m rows (eq's) and n columns (variable) where Ax>b; each row in A has a specific value in b. I want to add a constraint related to the sum of the elements in a certain column to be greater than a value (to be added to the end of b). In other words, a certain variable (ex: x1) should exist in the equations no more than certain times given by the corresponding b. Is it possible to do so? I have read some papers have solved the same problem but without details. Any idea? Thanks in advance
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Torsten il 16 Gen 2017
But the matrix A is given, I guess, and the elements of A determine whether x1 is present in an equation or not. So how should it be possible to deduce a constraint for what you are asking for ?
Best wishes
Torsten.
Ismaeel il 16 Gen 2017
Modificato: Ismaeel il 16 Gen 2017
Thanks Torsen... Yes, that's right, A is given. But, in MILP problems, one can add auxiliary variables that choose the rows (or even columns) that optimize the problem. Say, you want to ask Matlab that either equation 1 is correct or equation2 but not both. Matlab will choose the best one that minimizes the total cost. However, I can not apply this idea in Matlab.

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### Risposte (1)

Alan Weiss il 16 Gen 2017
You might be able to use the formulation of semicontinuous constraints in this example. Or the Set the Generator Startup Variables idea.
Good luck,
Alan Weiss
MATLAB mathematical toolbox documentation
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Ismaeel il 17 Gen 2017
Thanks Alan

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