Constrained Nonliner Curve Fit Error -20003 help

[zoomsky1988]

Hello.

I use Constrained Nonliner Curve Fit.vi to fit a customed function, just in the following picture 1. The initial paraments are exactly right, but it always stopped by a error -20003,it says "The number of samples must be >0",just as the picture 2.

What should I do to correct it? Thanks!

[altenbach]

Can you attach your code and some sample data? How big is the [X] array? The [a] array?

Does it work if you remove the partial derivatives calculation? (LabVIEW will automatically substitute numerical derivatives).

(The way you index into [a] seems incredibly convoluted. Couldn't you simply reshape into four columns and autoindex on a FOR loop?)