Another tip: you’ll get more attention from people with the right expertise to help with your problem if you edit your Topic title to be a little more specific — e.g., “Programming a linear model with constraints”.
Even better would be “Programming a linear model with constraints using [name of package or function you are trying to use]”
(If you’re not sure how to edit your Topic, there’s a FAQ for that: FAQ: How do I edit my Topic or Post?)