Please help on this Lev-Mar problem

Question

Hi,
I have two acquisition data sources that need
to be fitted. Then the fitted parameters are
passed along with data for further processing.
As the data is heardware generated, I made a
similar 'signal generator' to present very closely
the problem.
===Please see the attached vi file===
As you can see, these two Lev-Mar's function
/ derivatives are obviously different. We can edit
the fuction / derivative node. But the problem
is that when one is edited, the other changes too.
Anyways, we can NOT have two different functions.
My question is: How to have two different function
/ Deveritives here?
By the way, how to replace the MatLab box into
function node in my attached example?
I can 'wire' the out
put to next if it's a
function node. It says the type of variables are
different (output is a real instead of array).
Attachments:
Lev-Mar-Question2.vi ‏99 KB

Answer 1

You have a few options for multiple function/derivatives.
1. If you can express the model functions using the formula string syntax, then you might consider using the "Levenberg Marquardt.vi". Unfortunately the Levenberg-Marquardt.vi does not allow the specification of the derivative of the model function and always uses numerical derivatives. It is also somewhat slower than the "Nonlinear Lev-Mar Fit.vi".
2. You could also save a copy of the "Nonlinear Lev-Mar Fit.vi" using a different name, and also the "Lev-Mar ABX.vi" and "Target Fnc & Deriv Nonlin.vi" with different names. Then you would have a different set of VIs to implement the curve fitting on two different models. This is ugly, but would work.
3. You could modify the "Nonlinear Lev-Mar
Fit.vi", "Lev-Mar ABX.vi", and "Target Fnc & Deriv Nonlin.vi" to accept/pass VI references. The "Target Fnc & Deriv Nonlin.vi" would then perform a call by reference to a VI that you wrote implementing the current model function.
To replace the Matlab script node place the formula node inside a for-loop. The for-loop will auto-index the x and t arrays, and auto-build the y-array.