How is the residual in lsqnonlin calculated?

Does anyone know how's the residual being calcualted in lsqnonlin function?

I am interested to know the formula.

Is it : res = sum(fun(x).^2) at x?

Where fun is the function you are trying to minimize.

[Torsten]

5th line from above under

https://de.mathworks.com/help/optim/ug/lsqnonlin.html

But as a user of lsqnonlin, you have to supply the residual vector as

res(i) = f_i(x)

where f_i(x) is the i-th function you want to zeroize.

[John D'Errico]

Exactly. lsqnonlin does not calculate any residual. YOU calculate it, and return that to lsqnonlin, via your objective function.