Fitting Fraunhofer Diffraction Data

[LogicalTime]

1. The problem statement, all variables and given/known data
Is there a good way to do a fit. The fft looks simple:

I am trying to fit data from my experiment to the very nonlinear nested sine function given as equation 3 here:
http://www.physics.umd.edu/courses/Phys375/HillSpring10/Labs/Lab5Diffraction.pdf



2. Relevant equations
see above


3. The attempt at a solution
I am using matlab, the model function is crazy! Though the data looks good in fourier space.

[Rajini]

Try gnuplot, all in all it does a good fit.
it is just few minutes to do it. If you need help supply your data with the model function, i can try.
good luck