[Help-gsl] fitting 3-peak gauss

[Hinxx]

Hi all,

I'm new to GSL and numerical methods so please bear with me. I'm using 
GSL-2.1.

I'm trying to fit a 3-peak gaussian curve onto experiment data that I 
have (800W5-95kv_ROI.txt).
I started from expfit.c and nlfit.c and modified the code to handle 
gauss curve.
For my initial tests I also used code/data from test_gaussian.c. I've 
played around with the test set and managed to get proper amplitude, 
sigma and peak location(s), also when extending test set to hold three 
peaks (copies of first) and code to handle three peaks.

When using the real data of some 240 points, I'm seeing weird behavior. 
Solver bails out after 1st iteration and I get my initial guessed 
parameters back, unchanged.

If I fiddle with the data set a bit to make all the points between the 
peaks near zero I get better results, bat still good enough.

Maybe it is worth noting that I also have some sample Matlab code that 
manages to find the fit on the presented data set. It is using code from 
http://www2.imm.dtu.dk/projects/immoptibox/.

I'm attaching the modified GSL code and real data set if someone might 
be able to help out.

Thanks in advance,
Hinko

800W5-95kv_ROI.txt
Description: Text document

expfit.c
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Makefile
Description: Text document

nlfit.c
Description: Text Data

output.txt
Description: Text document