fitting

[Vladimir77777]

Hello,

 is it possible to fix a few coefficients during fitting, not to change them,  but  continue to find other coefficients?

Thanks, Vladimir 

[altenbach]

Yes.

What fitting tools do you use? Please show us some simplified code.

You can use or also read some of the discussion here. You could also use "Constrained nonlinear curve fit" an constrain some parameters to an infinitely small interval (i.e. upper=lower).