Linear constraints using lsqnonlin

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!

[Torsten]

A system of 3 equations in 3 unknowns usually has a unique solution.

So how can you put constraints on the solution ?

Do you want the 3 nonlinear equations only approximately to be satisfied ?

[Walter Roberson]

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.

Answer 1

[Walter Roberson]

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.

[Luca Vergani]

Thanks a lot

[Matt J]

Or rather minimize norm( F(x,y,z) )^2 to ensure differentiability of the objective.