[R] nls.lm

[Berend Hasselman]

> On 19 Oct 2016, at 14:09, Mike meyer <1101011 at gmx.net> wrote:
> 
> @pd: you know that a System of equations with more variables than equations is always solvable
> and if a unique solution is desired one of mimimal norm can be used.
> 

Not true.

Take the system with 3 variables and 2 equations

x+y+z = 3
x+y+z = 4

This does not have a solution.
See https://en.wikipedia.org/wiki/Consistent_and_inconsistent_equations

Berend

> According to "Methods for nonlinear least squares problems" by Madsen, Nielsen and Tingleff the LM-algorithm
> solves Systems of the form 
>                            [J(x)'J(x)+\mu*I]x=...
> with \mu>0 so that the Matrix on the left is always positive definite, especially nonsingular.
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.