Advance Curve Fitting Non Linear

[chtan23]

I have a problem with my non linear curve fitting program

I have attached below my program.

the equation used has y on both on the left and right hand side of the main equation

shown below

y = 3.4 - 6E-10*((exp(1.602 177E-19 *(x+(y*a))/(1.380 6505E-23 *(273+25)))-1) -((x+y*a)/b))

the program does not run and the a and b coeefficient could be determine.

I want to place IL, T and Isc as variable numbers

how to place a input on the front panel to insert the value for Isc and T and IL if this equation is used in the string constant

This makes the equation

y = Isc- IL*((exp(1.602 177E-19 *(x+(y*a))/(1.380 6505E-23 *(T)))-1) -((x+y*a)/b))

Download File:post-5613-1153226107.vi

[chtan23]

No one is able to do it ?

OR advice me ?

I have added in the datas required

[crelf]

No one is able to do it ?

OR advice me ?

I have added in the datas required

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[AnalogKid2DigitalMan]

Related discussion here

http://forums.ni.com/ni/board/message?boar...ding&page=1

[ahlers01]

No one is able to do it ?

OR advice me ?

I have added in the datas required

I had a look at your equation. If I read it correctly, you can substitute z:=x+a*y and then bring the equation to the form x=f(z).

You could then try to use this for non-linear fitting, treating x as the dependent and z as the independent variable.

Also I would recommend you normalize your values in such a way that reasonably sized coefficients occur, not ones which differ by 23 orders of magnitude. That would probably help to avoid numerical errors

-Franz