Linear constraints using lsqnonlin

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Hi, I'm solving a non-linear system of 3 equations in 3 unkowns:
I'm using lsqnonlin to solve it:
lambda = lsqnonlin(F,lambda0,lb,ub,options);
Moreover, I need to add some constraints to the variables:
How can pass this constraints to the solver?
Thanks in advance!
Walter Roberson
Walter Roberson on 28 Sep 2022
A system of 3 equations in 3 unknowns usually as a unique solution.
That is not generally the case for nonlinear systems. For example 3 curved surfaces might intersect at multiple locations and the constraints could narrow the result down to one particular quandrant.

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Accepted Answer

Walter Roberson
Walter Roberson on 28 Sep 2022
lsqnonlin() does not support constraints other than upper bound and lower bound.
I suggest you minimize the norm() of F(x,y,z)-lambda0 using fmincon() as you can supply linear inequality constraints for that.
Matt J
Matt J on 30 Sep 2022
Or rather minimize norm( F(x,y,z) )^2 to ensure differentiability of the objective.

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