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[Help-gsl] fitting 3-peak gauss

From: Hinxx
Subject: [Help-gsl] fitting 3-peak gauss
Date: Mon, 21 Mar 2016 16:26:07 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

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

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

Thanks in advance,

Attachment: 800W5-95kv_ROI.txt
Description: Text document

Attachment: expfit.c
Description: Text Data

Attachment: Makefile
Description: Text document

Attachment: nlfit.c
Description: Text Data

Attachment: output.txt
Description: Text document

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