# Question:Nonlinear Fit with nonlinear parameters

## Question:Nonlinear Fit with nonlinear parameters

Maple

I trying to fit an Eckartfunction with 3 parameters to my curve I've calculated with gaussian03 (IRC).

my given points for the curve are:

data:=[[-2.09823, 0], [-1.99836, .10247e-2], [-1.89845, .22513e-2], [-1.79853, .37005e-2], [-1.69858, .53857e-2], [-1.59862, .73126e-2], [-1.49865, .94799e-2], [-1.39867, .11878e-1], [-1.29869, .14489e-1], [-1.1987, .17287e-1], [-1.09871, .202372e-1], [-.99872, .232958e-1], [-.89872, .264089e-1], [-.79873, .295126e-1], [-.69873, .325342e-1], [-.59874, .353951e-1], [-.49875, .38011e-1], [-.39875, .40295e-1], [-.29876, .421657e-1], [-.19877, .435571e-1], [-.9878e-1, .444241e-1], [0, .447462e-1], [.9876e-1, .44433522e-1], [.19875, .43623057e-1], [.29874, .42376069e-1], [.39873, .40771464e-1], [.49872, .38896537e-1], [.59872, .36840196e-1], [.69871, .34688203e-1], [.7987, .32516288e-1], [.89869, .30397633e-1], [.99867, .28390449e-1], [1.09865, .26542272e-1], [1.19861, .24888004e-1], [1.29855, .23448698e-1], [1.39845, .22231283e-1]]

The function I want to fit is: y=((A*exp((2*Pi*x)/L))/(1+exp((2*Pi*x)/L)))+((B*exp((2*Pi*x)/L))/(1+exp((2*Pi*x)/L))^2)

I need the values for A,B,L.

But they are nonlinear, so I can't get a fit with usual fitting commands in maple.

My question is: Is there an other possibility to solve my problem with maple?  (I've tried to fit it with Origin, but the parameters are not correct)

I thnak for any help

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