Lev-Mar Non-Linear Cuve Fitting:

[MatTech]

The equation I am solving for has nine variables. When I use real data derived from the response of elastomers under compression the vi is unable to converge. Or it does converge with an plotting a curve with an offset.

[Stu 708]

There can be multiple solutions to Lev-Mar that meet the convergance criteria. The initial guess of the parameters could make a big difference. When I used Lev-Mar before, I only had to approximate one (key) variable in order for it to converge nicely. Can you approximate any of the parameters? Give it a try.
Stu