Hello,
I might be a bit annoying regarding this problem and, therefore, I apologize

.
Here is a problem I struggled with for some time - without success.
The problem is quite frequent and requires the minimization of multivariable function:

There is the accompanied file -
NLMinimization.smI can not find the solution when the function S( b ) has to be minimized regarding to vector "b". You could see in the file that I did the linear fitting and it could serve as an initial guess for the nonliner fitting - this is a coomon thing. I tried the usual thing - finding the roots of the first derivatives of S( b ) on each element of vector "b" using roots or standard Newton-Raphson method. Whatever I tried regarding this, I failed. If someone is willing to try to solve this and will have success - I would be very grateful.
Regards,
Radovan
When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"