No need to modify the curve fitting VIs. There are actually two steps. First, concatenate the J and V arrays using 'build array'. Make sure to right-click on 'build array' and choose concatenate. This concatenated array is passed to the 'Nonlinear Curve Fit.vi' as the X input. I would recommend using the VI reference interface, and not the formula string. Create a model VI using the template located at: ...\vi.lib\gmath\NumericalOptimization\LM model function and gradient.vit
Inside your new model VI there is an X input array. This is the array that you will have to split using the 'Split 1D Array' primitive.
Take a look at the following example: ...\examples\Mathematics\Fitting\Ellipse fit.vi
On the diagram notice the use of interleave 1D array. Instead of interleaving, it may be more efficient to use the build array. Now open the model VI for the ellipse (...\examples\Mathematics\Fitting\support\ellipse model.vi). Notice the use of decimate 1D array. Instead of decimate, you would use Split 1D Array.
-Jim
